SD2-592: Exception thrown when trying to copy a file

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@853 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/Main/Base/Project/Src/Gui/Pads/ProjectBrowser/TreeNodes/DirectoryNode.cs

@@ -17,7 +17,8 @@ using ICSharpCode.Core;
 
 namespace ICSharpCode.SharpDevelop.Project
 {
-	public class FileOperationClipboardObject : System.MarshalByRefObject
+	[Serializable]
+	public class FileOperationClipboardObject
 	{
 		string fileName;
 		bool   performMove;