Meant to add that in the next field it lists the full path to the .vmx file using the full datastore ref. ID
We're on ESXi 5.1 Update 1, btw.
I'm not sure whether I fully understand the current situation. Anyway, does the VM have an active snapshot?
Have you got a CD or ISO mounted on that VM? I had 3 doing that, 2 had an ISO mounted, one was vCenter! Still haven't resolved that one!