I've had this same problem with ME for some time. I found a patch on the Microsoft website that seemed to cure things, but only for a while! After a couple of months the problem returned. I then discovered that System Restore was deleting all of my own manual restore points that I had created.
To be honest I've found it to be a useless bit of kit overall and hasn't woked for me when I've really needed it, so I don't bother with it any more.
From what I understand this is not an uncommon problem.