Pondus
8
first, what AV did you have before installing avast ?
did you remove it before installing avast ?
did you run a removal tool to clear any leftover files ?
run and reboot - Uninstallers – Security Software
http://singularlabs.com/uninstallers/security-software/
or try a new clean install of avast
remove with this and reboot - Uninstall Utility http://www.avast.com/en-eu/uninstall-utility
then install again and reboot