To my mind it is strange to find a virus in your system volume information folder without first having found one in the systems folders and deleted it.
Viruses that are deleted (or possibly moved) from the system folders are in effect protected by windows system restore (in its wisdom), a copy is saved as a _restore point in the system volume information folder, just in case you made a mistake or want to restore the file. So if that didn't happen then I can't see how a restore point can become infected.
So I suggest you email it to avast from the chest and say you suspect it to be a False Positive and give some info and possibly a link to this thread.