I recommend a full uninstall and install from scratch.
(By doing this you will lose any Avast settings you have saved, plus anything in the quarantine.)
-Download the Avast uninstall utility, http://www.avast.com/eng/avast-uninstall-utility.html
It may also be worthwhile to download the appropriate Kaspersky removal tool, http://support.kaspersky.com/faq/?qid=208279463
-If you don't already have it, download the latest Avast install. http://www.avast.com/eng/download-avast-home.html
-Disconnect from the net,
-Right click the tray icon, go to program settings>troubleshooting, and select "disable Avst self defence module".
-Right click the tray icon, select "stop on access protection" and "ok" out.
-Uninstall from the control panel.
-Reboot, run the Avast uninstall utility.
-Run the Kaspersky uninstall utility, reboot.
-Install Avst antivirus. (You may wish to skip the boot scan recommended as part of a first install- this takes a while.)
-Reconnect to the net, check for database updates.
-Post back and tell us if the problem is solved.
This should work.