When I try and move any sub-folders in a particular branch of the Media tree I am getting a NullReferenceException in the move dialog box.

Media Section
- Branch 1
-- SubFolder1
-- SubFolder2

- Branch 2
-- SubFolder1
-- SubFolder2

With a tree structure like this if I try and move SubFolder1 from Branch 1 anywhere the dialog box appears with the below stack trace.  Moving anything in Branch 2 works fine and I can move nodes around in that branch and into Branch 1.

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.dialogs.moveOrCopy.CheckPermissions(CMSNode node, IAction currentAction, Char actionLetter) +53
   umbraco.dialogs.moveOrCopy.ValidAction(Char actionLetter) +156
   umbraco.dialogs.moveOrCopy.Page_Load(Object sender, EventArgs e) +1440
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   umbraco.BasePages.BasePage.OnLoad(EventArgs e) +14
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

Version Information: 

• .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1
• Umbraco 4.7.0

Has anyone else seen this problem before?  I can't replicate it in a clean install.

Regards

Evan