try doing a new clean install…

follow instructions and run it for all avast versions ever installed on computer. http://www.avast.com/uninstall-utility

download and reinstall. http://www.avast.com/download-software

any change?

and you have of course removed any previous used or factory installed AV before installing avast ?

General: Uninstalling a third-party antivirus software. http://www.avast.com/faq.php?article=AVKB11