Duplicate menu items/ "unable to move that item" message

[alto-pete]

I have a problem with my new X30 - have just transferred data from my 'old' X3 and wanted to rejig my menu items but have discovered many of the items under Settings/ Menus are duplicated (with one of the duplicates checked) - when I try to uncheck the checked duplicate item I get the message in the heading. This is really annoying and I wondered if anyone else had come across this problem

Thanks

Peter