Here is a VMWare Server technical tidbit I have run into before and confirmed. If you use snapshots in VMWare server there is an issue that can pop-up and simply requires some patience.

The scenario is you have an old snap shot of a VM and you want to purge it. First off, this is a good practice. Old snap shots cause you to maintain two VMDK files (virtual disk files) so it appears to cause a small performance hit. The more disks the bigger the hit. If snaps are part of your strategy then I strongly recommend that they are a secondary method of backing up your server. I have been burned more then once on snap shots. In my opinion they are best used for immediate changes that you may need to reverse in the very short term. Otherwise a more robust backup should be considered.

Anyway's, back to the topic. When you take the VM down and select the option to remove the snapshot nothing appears to be going on. Shortly thereafter your console gives you an error 511 and you can no longer work on anything. You wait a bit and still nothing. Here is an important piece of advice if you do not want to corrupt the whole VM. Don't shut down the server or any VMWare services. The VM VMDK files are being integrated and any interruption will make the unusable ever again. I found a way to monitor when the process is complete. Start your task manager. In the processes list you will see a process running called "snhelper.exe". That is the process working on your VM

and combining the VMDK files. Just wait for that process to complete. When it is done the console returns to normal function and your VM is ready to be restarted. Even though the console is unavailable, other VM's running on your host will continue to run and are unaffected by the console being unavailable for use.

In summary, do not depend on snap shots as your only back-up and do not let your snap shots age indefinitely. Life will be much simpler.