"Cannot open the disk 'XXX' or one of the snapshot disks it depends on. reason: failed to lock the file.

I created five virtual machines in VMware server 5.0. I then tried to load them in VMware workstation 6.0. One loaded succesfully the other four all gave me the message:

"Cannot open the disk 'XXX' or one of the snapshot disks it depends on. reason: failed to lock the file.

I have tried deleting all the .lck files AND switch off all the VMware services but the error still persists.