Black screen after logging out/switching users and attempting to log in again.

Hello. I'm having the following issue on Vista 32bit Home Premium:

(1) I log into an account.
(2) I log out of that account (or hit switch users.)
(3) I log into a different account.
(4) After Vista authenticates the account, I get a black screen.

If I CTRL+ALT+DEL, I can get to the Task Manager. Explorer.exe does not load. I can hit "run" and manually start explorer.exe but it doesn't help. Does anyone know a workaround for this? The problem occurs only after I switch user accounts, the accounts work fine on their own if they are logged into first.

Some other information:
- Dell Vostro 2510
- Latest nVidia Drivers

The only "fix" that I've found for the Black Screen error is to use System Restore to go back to a time before it started.

AFAIK, it's an issue in the registry and it has something to do with security settings (most times). Beyond that, there's just too many variables to determine what the cause it.

At work, if we don't have a Restore Point to fix it - we wipe the hard drive and reinstall Windows. Customers don't want to pay us (by the hour) to spend weeks fooling around with their systems - only to find out we can't fix it.