welcome to the forum.
i suggest you try a clean installtion from scratch of avast and see if that could solve your problem.
download the latest version of avast from http://www.avast.com/en-se/free-antivirus-download
download the uninstall tool and run it.
http://www.avast.com/en-se/uninstall-utility
reboot your system.
do a registry clean with ccleaner to clean any lef over files of avast.
http://filehippo.com/download_ccleaner/
install the latest version of avast, registry the program.
good luck and let us know if you need more support.