If it has gone back to an earlier time (like last good boot or system restore) there is every possibility that avast could have become corrupt.
- Try a repair of avast:
XP - Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.
Vista, win7 - Control Panel, Programs & Features, uninstall a program, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.
You may need to reboot after the repair. This has in the past resolved this out of sync issue between reported and actual VPS version.
- If that doesn't work try, uninstall, reboot, install, reboot.