When we (you) moved the files to the backup folder only the file pointer (i.e. FAT entry) was modified, but the file itself was not accessed. There might still be a lock on this file or a possible VMFS issue which causes this error message!? This would also explain why the snapshots could not be removed.
Check the files to ensure none of it has a current time stamp, then run the touch <filename> command for each of the files to find out which one causes the issue. (see http://kb.vmware.com/kb/10051)
Unless you already did, you could try to restart the "Management Agents" - from the DCUI or by running /sbin/services.sh restart - to see if this resolves the issue. Before you try to restart the Management Agents make sure there's no application (e.g. backup) running which uses the services at the moment!
André