Everyone that works with virtual machines has seen this issue that when going back to an old snapshot the user domain account does not work anymore and the machine needs to be taken out of the domain and added again.
Fortunately there is a workaround for that taken from this Microsoft document - http://support.microsoft.com/kb/154501
This will not fix your existing VM's but will prevent the issue from showing again in the future.
Make sure to run these steps when building a new VM and only snapshoting it after that. From then on you can switch between any following snapshots without any AD issues.
For Windows 2000 and above
- Start Registry Editor. To do so, click Start, click Run, type regedit in the Open box, and then click OK.
- Locate and then click the following registry subkey:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters
- In the right pane, click theDisablePasswordChangeentry.
- On the Edit menu, click Modify.
- In the Value data box, type a value of 1, and then click OK.
- Quit Registry Editor.