System Restore is far from perfect and can have unexpected consequences.
Have you rebooted since using system restore ?
Try a repair of avast. Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.
If that doesn't work I think you are looking at a clean reinstall:
Download the latest version of avast, 5.0.462
http://www.avast.com/free-antivirus-download and save it to your HDD, somewhere you can find it again (if you didn't save your last download). Use that when you reinstall.
Download the avast! Uninstall Utility, aswClear5.exe
find it here and save it to your HDD (it has uninstall tools for both 4.8 and 5.0).
- 1. Now uninstall (using add remove programs, if you can't do that start from the next step), reboot.
- 2. run the avast! Uninstall Utility from safe mode, first for 4.8 if previously installed and then for 5.0, once complete reboot into normal mode.
- 3. install the latest version, reboot.