Just like you said, gives you an error about a problem with the registry and it wants to restore a backup, then it reboots and the same error comes up, just won't go away.
We had users simply move the error window off the screen and all was well. We tried everything, the only way to fix it was to format and re-install. We are still not sure what caused it, but it did start when we implemented a Logon Policy from our BDC. Out of 4 almost identically setup PC's, 2 of them did this. Crazy ****, drives my nuts sometimes...