Most viruses can infect restore points nowadays, but it's usually the 1st restore point (although I'm sure some are quite capable of infecting all of them). I usually tell people when they are restoring due to a virus, to go the 2nd, or better yet, 3rd restore point.
As Dinish pointed out, if you have a hidden partition somewhere on the system, usuall written by a rootkit, a system restore doesn't do any good.