Windows 7 restore problem

I had a reason ( not virus related ) to want to roll back my Windows 7 to a restore point from a day ago. Ran system restore and it seemed to run fine, rebooted and then after the reboot I got a message that the restore point had been corrupted and thus the restore canceled. Huh. So I went back in and restored to a point a few days earlier. Same thing : seemed to do the whole restore process then after the reboot the message that the restore point was corrupted.

Any ideas what is going on here?