There is a command called "Remove Reservation" on the File menu (Under "File Control" I think). This is for administrators only and is like an Undo Check out.
Director of Product Lifecycle Management
I have experienced the same problem here.
I have used the "Remove Reservation" option under the file menu to resolve my issue which was the same, but does this realyl mean that for an "Admin User" the "Role" for Undo Checkout (All Users) does not really work?