It may be worth doing a clean install of Avast

Download Uninstall Utility to your Desktop.
Download the correct version of Avast
Avast Free

Disconnect from the net
Uninstall Avast via control panel

[]Run aswClear
[
]It will offer to reboot to safe mode … Accept that

https://dl.dropbox.com/u/73555776/aswclear.JPG

[*]Once it has rebooted to safe mode
[*]In the Select Product to Uninstall dropdown choose the version of Avast that is on your system.
[*]Press Uninstall
[*]Once complete reboot your system to Normal Mode
[*]Reinstall Avast