Snapshot Error in parallels 3 5626 build

I reinstalled my vm machine from a time machine back up and tried to revert to a snapshot i had but keep getting the error message

An error occurred during reverting to snapshot. The selected snapshot doesn't exist.

Even though the snapshot does exist, and is showing in snapshot manager, also the snapshot folder has the relevent snapshot png and associated files.

Why can't I revert back to it ?

Any help would be appreciated.