You are running ESX and have a VDR or 2 setup to do backups? Somewhere the VDR was rebooted or stopped working during backup and now has left snapshots on you VMs. You try to manually remove the snapshots and BAMB!
Error: Remove all snapshots Unable to access file <unspecified filename> since it is locked.
Here is how to fix it:
Shutdown your VDRs and then try to remove your snapshots. If they fail to remove then take another snapshot then try using the removing all “Delete All” function. This is a safe process at this point, the delta files are not deleted until the successful merge of the delta and the flat file. This means if it fails you should still be no worse off than you are currently, no data was lost.
Now once all snaps are deleted, you may get a similar error trying to start your VDR. The VDR mounts the VM disks and does it’s backup . The mounts may still exist and this will cause the VDR issues booting. Edit the settings in the VDR and look for Hard disks 2+ and remove them from the VM (Do NOT Delete Then!!! Just Remove them leaving HardDisk1) .
Once all but HardDisk1 has been removed from the VDR VM then reboot the VDR and you should be ready to start backing up again.
I hope this helps someone out there..