diff --git a/src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ChangeMarkerMargin.cs b/src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ChangeMarkerMargin.cs
index 80902ea5df..b47bc3b841 100644
--- a/src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ChangeMarkerMargin.cs
+++ b/src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ChangeMarkerMargin.cs
@@ -15,6 +15,7 @@ using ICSharpCode.AvalonEdit.Rendering;
 using ICSharpCode.Core;
 using ICSharpCode.SharpDevelop.Editor;
 using ICSharpCode.SharpDevelop.Widgets.MyersDiff;
+using ICSharpCode.NRefactory.Editor;
 
 namespace ICSharpCode.AvalonEdit.AddIn
 {
@@ -229,7 +230,7 @@ namespace ICSharpCode.AvalonEdit.AddIn
 					differ.editor.Visibility = Visibility.Collapsed;
 					differ.copyButton.Visibility = Visibility.Collapsed;
 				} else {
-					var baseDocument = new TextDocument(changeWatcher.BaseDocument);
+					var baseDocument = new ReadOnlyDocument(changeWatcher.BaseDocument);
 					if (differ.editor.SyntaxHighlighting != null) {
 						var mainHighlighter = new DocumentHighlighter(baseDocument, differ.editor.SyntaxHighlighting.MainRuleSet);
 						var popupHighlighter = differ.editor.TextArea.GetService(typeof(IHighlighter)) as DocumentHighlighter;
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingManager.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingManager.cs
index ee1d5167c0..b6598c12c4 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingManager.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingManager.cs
@@ -8,7 +8,7 @@ using System.Diagnostics;
 using System.IO;
 using System.Xml;
 
-using ICSharpCode.AvalonEdit.Utils;
+using ICSharpCode.NRefactory.Utils;
 
 namespace ICSharpCode.AvalonEdit.Highlighting
 {
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj
index 9abcd2b944..d4d293044b 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj
@@ -343,9 +343,6 @@
     </Compile>
     <Compile Include="TextViewPosition.cs" />
     <Compile Include="Utils\Boxes.cs" />
-    <Compile Include="Utils\BusyManager.cs">
-      <DependentUpon>ObserveAddRemoveCollection.cs</DependentUpon>
-    </Compile>
     <Compile Include="Utils\CharRope.cs" />
     <Compile Include="Utils\CompressingTreeList.cs" />
     <Compile Include="Utils\Constants.cs" />
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Utils/BusyManager.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Utils/BusyManager.cs
deleted file mode 100644
index f5c4047b71..0000000000
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Utils/BusyManager.cs
+++ /dev/null
@@ -1,55 +0,0 @@
-// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
-// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
-
-using System;
-using System.Collections.Generic;
-
-namespace ICSharpCode.AvalonEdit.Utils
-{
-	/// <summary>
-	/// This class is used to prevent stack overflows by representing a 'busy' flag
-	/// that prevents reentrance when another call is running.
-	/// However, using a simple 'bool busy' is not thread-safe, so we use a
-	/// thread-static BusyManager.
-	/// </summary>
-	static class BusyManager
-	{
-		public struct BusyLock : IDisposable
-		{
-			public static readonly BusyLock Failed = new BusyLock(null);
-			
-			readonly List<object> objectList;
-			
-			public BusyLock(List<object> objectList)
-			{
-				this.objectList = objectList;
-			}
-			
-			public bool Success {
-				get { return objectList != null; }
-			}
-			
-			public void Dispose()
-			{
-				if (objectList != null) {
-					objectList.RemoveAt(objectList.Count - 1);
-				}
-			}
-		}
-		
-		[ThreadStatic] static List<object> _activeObjects;
-		
-		public static BusyLock Enter(object obj)
-		{
-			List<object> activeObjects = _activeObjects;
-			if (activeObjects == null)
-				activeObjects = _activeObjects = new List<object>();
-			for (int i = 0; i < activeObjects.Count; i++) {
-				if (activeObjects[i] == obj)
-					return BusyLock.Failed;
-			}
-			activeObjects.Add(obj);
-			return new BusyLock(activeObjects);
-		}
-	}
-}
diff --git a/src/Main/Base/Project/Src/Util/ExtensionMethods.cs b/src/Main/Base/Project/Src/Util/ExtensionMethods.cs
index c6b690dd83..0df56d8452 100644
--- a/src/Main/Base/Project/Src/Util/ExtensionMethods.cs
+++ b/src/Main/Base/Project/Src/Util/ExtensionMethods.cs
@@ -86,7 +86,7 @@ namespace ICSharpCode.SharpDevelop
 						else
 							Core.MessageService.ShowException(t.Exception);
 					}
-				});
+				}, TaskContinuationOptions.OnlyOnFaulted);
 		}
 		
 		/// <summary>