diff --git a/ClosedXML/Excel/Cells/XLCell.cs b/ClosedXML/Excel/Cells/XLCell.cs
index d667470..9b96722 100644
--- a/ClosedXML/Excel/Cells/XLCell.cs
+++ b/ClosedXML/Excel/Cells/XLCell.cs
@@ -966,8 +966,6 @@
             set
             {
                 _formulaR1C1 = XLHelper.IsNullOrWhiteSpace(value) ? null : value;
-
-// FormulaA1 = GetFormulaA1(value);
             }
         }
 
@@ -1761,9 +1759,10 @@
             {
                 var matchString = match.Value;
                 var matchIndex = match.Index;
-                if (value.Substring(0, matchIndex).CharCount('"') % 2 == 0)
+                if (value.Substring(0, matchIndex).CharCount('"') % 2 == 0
+                    && value.Substring(0, matchIndex).CharCount('\'') % 2 == 0)
                 {
-// Check if the match is in between quotes
+                    // Check if the match is in between quotes
                     sb.Append(value.Substring(lastIndex, matchIndex - lastIndex));
                     sb.Append(conversionType == FormulaConversionType.A1ToR1C1
                                   ? GetR1C1Address(matchString, rowsToShift, columnsToShift)
diff --git a/ClosedXML/Excel/Ranges/XLRangeBase.cs b/ClosedXML/Excel/Ranges/XLRangeBase.cs
index 3484ed6..60d12d4 100644
--- a/ClosedXML/Excel/Ranges/XLRangeBase.cs
+++ b/ClosedXML/Excel/Ranges/XLRangeBase.cs
@@ -1388,7 +1388,7 @@
                     {
                         var modelFirstColumn = model.FirstCellUsed(true);
                         var modelLastColumn = model.LastCellUsed(true);
-                        if (modelLastColumn != null)
+                        if (modelFirstColumn != null && modelLastColumn != null)
                         {
                             Int32 firstCoReturned = modelFirstColumn.Address.ColumnNumber
                                                     - model.RangeAddress.FirstAddress.ColumnNumber + 1;
diff --git a/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs b/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs
index 0f1c4ca..356424c 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.NestedTypes.cs
@@ -99,7 +99,7 @@
                 {
                     _relIds.Add(relType, new List<String>());
                 }
-                _relIds[relType].AddRange(values);
+                _relIds[relType].AddRange(values.Where(v => !_relIds[relType].Contains(v)));
             }
             public void Reset(RelType relType)
             {
@@ -147,9 +147,5 @@
             public IXLStyle Style;
         }
         #endregion
-
-        
-        
-       
     }
-}
\ No newline at end of file
+}
diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index 8dd7f14..1a4f3bc 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -578,24 +578,36 @@
                 sheet.Name = wks.Name;
             }
 
-            foreach (var xlSheet in
-                WorksheetsInternal.Cast<XLWorksheet>().Where(s => s.SheetId == 0).OrderBy(w => w.Position))
+            foreach (var xlSheet in WorksheetsInternal.Cast<XLWorksheet>().OrderBy(w => w.Position))
             {
-                var rId = context.RelIdGenerator.GetNext(RelType.Workbook);
-
-                while (WorksheetsInternal.Cast<XLWorksheet>().Any(w => w.SheetId == Int32.Parse(rId.Substring(3))))
+                string rId;
+                if (xlSheet.SheetId == 0)
+                {
                     rId = context.RelIdGenerator.GetNext(RelType.Workbook);
 
-                xlSheet.SheetId = Int32.Parse(rId.Substring(3));
-                xlSheet.RelId = rId;
-                var newSheet = new Sheet
-                {
-                    Name = xlSheet.Name,
-                    Id = rId,
-                    SheetId = (UInt32)xlSheet.SheetId
-                };
+                    while (WorksheetsInternal.Cast<XLWorksheet>().Any(w => w.SheetId == Int32.Parse(rId.Substring(3))))
+                        rId = context.RelIdGenerator.GetNext(RelType.Workbook);
 
-                workbook.Sheets.AppendChild(newSheet);
+                    xlSheet.SheetId = Int32.Parse(rId.Substring(3));
+                    xlSheet.RelId = rId;
+                }
+                else
+                {
+                    rId = String.Format("rId{0}", xlSheet.SheetId);
+                    context.RelIdGenerator.AddValues(new List<string> { rId }, RelType.Workbook);
+                }
+
+                if (!workbook.Sheets.Cast<Sheet>().Any(s => s.Id == rId))
+                {
+                    var newSheet = new Sheet
+                    {
+                        Name = xlSheet.Name,
+                        Id = rId,
+                        SheetId = (UInt32)xlSheet.SheetId
+                    };
+
+                    workbook.Sheets.AppendChild(newSheet);
+                }
             }
 
             var sheetElements = from sheet in workbook.Sheets.Elements<Sheet>()
diff --git a/ClosedXML/Extensions.cs b/ClosedXML/Extensions.cs
index 1a33550..a37daf3 100644
--- a/ClosedXML/Extensions.cs
+++ b/ClosedXML/Extensions.cs
@@ -75,10 +75,10 @@
             HashSet<T> distinctItems = new HashSet<T>();
             foreach (var item in source)
             {
-                if (distinctItems.Contains(item))
-                    return true;
-                else
-                    distinctItems.Add(item);
+              if (!distinctItems.Add(item))
+              {
+                return true;
+              }
             }
             return false;
         }
diff --git a/ClosedXML_Tests/ClosedXML_Tests.csproj b/ClosedXML_Tests/ClosedXML_Tests.csproj
index f1c0f09..89a0eff 100644
--- a/ClosedXML_Tests/ClosedXML_Tests.csproj
+++ b/ClosedXML_Tests/ClosedXML_Tests.csproj
@@ -78,6 +78,7 @@
     <Compile Include="Excel\Loading\LoadingTests.cs" />
     <Compile Include="Excel\PageSetup\HeaderFooterTests.cs" />
     <Compile Include="Excel\Ranges\UsedAndUnusedCellsTests.cs" />
+    <Compile Include="Excel\Saving\SavingTests.cs" />
     <Compile Include="XLHelperTests.cs" />
     <Compile Include="Excel\AutoFilters\AutoFilterTests.cs" />
     <Compile Include="Excel\CalcEngine\DateAndTimeTests.cs" />
@@ -249,11 +250,11 @@
     <EmbeddedResource Include="Resource\Examples\ConditionalFormatting\CFDataBar.xlsx" />
     <EmbeddedResource Include="Resource\Examples\ConditionalFormatting\CFIconSet.xlsx" />
     <EmbeddedResource Include="Resource\Examples\Ranges\SelectingRanges.xlsx" />
+    <EmbeddedResource Include="Resource\Misc\EmptyTable.xlsx" />
     <EmbeddedResource Include="Resource\Misc\TableWithCustomTheme.xlsx" />
     <EmbeddedResource Include="Resource\Examples\Ranges\AddingRowToTables.xlsx" />
     <EmbeddedResource Include="Resource\Examples\Misc\RightToLeft.xlsx" />
     <EmbeddedResource Include="Resource\Examples\PivotTables\PivotTables.xlsx" />
-    <None Include="Resource\Misc\WorkbookProperties.xlsx" />
     <None Include="packages.config" />
   </ItemGroup>
   <ItemGroup />
@@ -265,4 +266,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>
\ No newline at end of file
diff --git a/ClosedXML_Tests/Excel/Loading/LoadingTests.cs b/ClosedXML_Tests/Excel/Loading/LoadingTests.cs
index 5412c0a..3568007 100644
--- a/ClosedXML_Tests/Excel/Loading/LoadingTests.cs
+++ b/ClosedXML_Tests/Excel/Loading/LoadingTests.cs
@@ -8,7 +8,7 @@
 
 namespace ClosedXML_Tests.Excel
 {
-    // Tests in this fixture test only the successful loading of existing Excel files, 
+    // Tests in this fixture test only the successful loading of existing Excel files,
     // i.e. we test that ClosedXML doesn't choke on a given input file
     // These tests DO NOT test that ClosedXML successfully recognises all the Excel parts or that it can successfully save those parts again.
     [TestFixture]
@@ -19,7 +19,8 @@
         {
             var files = new List<string>()
             {
-                @"Misc\TableWithCustomTheme.xlsx"
+                @"Misc\TableWithCustomTheme.xlsx",
+                @"Misc\EmptyTable.xlsx"
             };
 
             foreach (var file in files)
@@ -27,5 +28,17 @@
                 TestHelper.LoadFile(file);
             }
         }
+
+        [Test]
+        public void CanLoadAndManipulateFileWithEmptyTable()
+        {
+            using (var stream = TestHelper.GetStreamFromResource(TestHelper.GetResourcePath(@"Misc\EmptyTable.xlsx")))
+            using (var wb = new XLWorkbook(stream))
+            {
+                var ws = wb.Worksheets.First();
+                var table = ws.Tables.First();
+                table.DataRange.InsertRowsBelow(5);
+            }
+        }
     }
-}
\ No newline at end of file
+}
diff --git a/ClosedXML_Tests/Excel/Misc/FormulaTests.cs b/ClosedXML_Tests/Excel/Misc/FormulaTests.cs
index 9d7cc15..9e1e695 100644
--- a/ClosedXML_Tests/Excel/Misc/FormulaTests.cs
+++ b/ClosedXML_Tests/Excel/Misc/FormulaTests.cs
@@ -18,5 +18,25 @@
             ws.Cell("A1").CopyTo("A2");
             Assert.AreEqual("B2", ws.Cell("A2").FormulaA1);
         }
+
+        [Test]
+        public void CopyFormulaWithSheetNameThatResemblesFormula()
+        {
+            using (var wb = new XLWorkbook())
+            {
+                IXLWorksheet ws = wb.Worksheets.Add("S10 Data");
+                ws.Cell("A1").Value = "Some value";
+
+                ws = wb.Worksheets.Add("Summary");
+                ws.Cell("A1").FormulaA1 = "='S10 Data'!A1";
+                Assert.AreEqual("Some value", ws.Cell("A1").Value);
+
+                ws.Cell("A1").CopyTo("A2");
+                Assert.AreEqual("'S10 Data'!A2", ws.Cell("A2").FormulaA1);
+
+                ws.Cell("A1").CopyTo("B1");
+                Assert.AreEqual("'S10 Data'!B1", ws.Cell("B1").FormulaA1);
+            }
+        }
     }
-}
\ No newline at end of file
+}
diff --git a/ClosedXML_Tests/Excel/Saving/SavingTests.cs b/ClosedXML_Tests/Excel/Saving/SavingTests.cs
new file mode 100644
index 0000000..22aa34a
--- /dev/null
+++ b/ClosedXML_Tests/Excel/Saving/SavingTests.cs
@@ -0,0 +1,30 @@
+using ClosedXML.Excel;
+using NUnit.Framework;
+using System.IO;
+
+namespace ClosedXML_Tests.Excel.Saving
+{
+    [TestFixture]
+    public class SavingTests
+    {
+        [Test]
+        public void CanSuccessfullySaveFileMultipleTimes()
+        {
+            using (var wb = new XLWorkbook())
+            {
+                var sheet = wb.Worksheets.Add("TestSheet");
+                var memoryStream = new MemoryStream();
+                wb.SaveAs(memoryStream, true);
+
+                for (int i = 1; i <= 3; i++)
+                {
+                    sheet.Cell(i, 1).Value = "test" + i;
+                    wb.SaveAs(memoryStream, true);
+                }
+
+                memoryStream.Close();
+                memoryStream.Dispose();
+            }
+        }
+    }
+}
diff --git a/ClosedXML_Tests/Resource/Misc/EmptyTable.xlsx b/ClosedXML_Tests/Resource/Misc/EmptyTable.xlsx
new file mode 100644
index 0000000..e902376
--- /dev/null
+++ b/ClosedXML_Tests/Resource/Misc/EmptyTable.xlsx
Binary files differ
diff --git a/ClosedXML_Tests/TestHelper.cs b/ClosedXML_Tests/TestHelper.cs
index 07576df..36b5933 100644
--- a/ClosedXML_Tests/TestHelper.cs
+++ b/ClosedXML_Tests/TestHelper.cs
@@ -90,12 +90,20 @@
 #pragma warning restore 162
         }
 
-        public static void LoadFile(string filePartName)
+        public static string GetResourcePath(string filePartName)
+        {
+            return filePartName.Replace('\\', '.').TrimStart('.');
+        }
+
+        public static Stream GetStreamFromResource(string resourcePath)
         {
             var extractor = new ResourceFileExtractor(null, ".Resource.");
+            return extractor.ReadFileFromResToStream(resourcePath);
+        }
 
-            string resourcePath = filePartName.Replace('\\', '.').TrimStart('.');
-            using (var stream = extractor.ReadFileFromResToStream(resourcePath))
+        public static void LoadFile(string filePartName)
+        {
+            using (var stream = GetStreamFromResource(GetResourcePath(filePartName)))
             {
                 var wb = new XLWorkbook(stream);
                 wb.Dispose();