See Vlk’s solution for this: http://www.avast.com/forum/index.php?board=2;action=display;threadid=1610;start=msg9952#msg9952

Other related threads:
http://forum.avast.com/index.php?board=2;action=display;threadid=2981
http://forum.avast.com/index.php?board=2;action=display;threadid=4039
http://forum.avast.com/index.php?board=2;action=display;threadid=3902
http://forum.avast.com/index.php?board=10;action=display;threadid=4590
http://forum.avast.com/index.php?board=10;action=display;threadid=5819

Hope this help :-[