naz@d3 ~ $ cat /etc/portage/patches/dev-util/monodevelop/Tb02.patch
diff -apurN ./src/addins/MonoDevelop.SourceEditor2/MonoDevelop.SourceEditor/CompileErrorTooltipProvider.cs ./src/addins/MonoDevelop.SourceEditor2/MonoDevelop.SourceEditor/CompileErrorTooltipProvider.cs
--- ./src/addins/MonoDevelop.SourceEditor2/MonoDevelop.SourceEditor/CompileErrorTooltipProvider.cs      2011-11-02 01:05:39.000000000 +0100
+++ ./src/addins/MonoDevelop.SourceEditor2/MonoDevelop.SourceEditor/CompileErrorTooltipProvider.cs      2011-12-10 15:20:57.205274180 +0100
@@ -43,8 +43,18 @@ namespace MonoDevelop.SourceEditor

                public TooltipItem GetItem (Mono.TextEditor.TextEditor editor, int offset)
                {
-                       ExtensibleTextEditor ed = (ExtensibleTextEditor) editor;
-                       return new TooltipItem (ed.GetErrorInformationAt (offset), editor.Document.GetLineByOffset (offset));
+                       ExtensibleTextEditor ed = editor as ExtensibleTextEditor;
+
+            if(ed==null)
+            return null;
+
+            string errorInformation=ed.GetErrorInformationAt (offset);
+
+            // If no error information were obtained, return.
+            if (string.IsNullOrEmpty(errorInformation))
+            return null;
+
+            return new TooltipItem (errorInformation, editor.Document.GetLineByOffset (offset));
                }

                public Gtk.Window CreateTooltipWindow (Mono.TextEditor.TextEditor editor, int offset, Gdk.ModifierType modifierState, TooltipItem item)
naz@d3 ~ $