I’m still having this problem using IE8 with avast 5.0.396! Anyone know any settings in IE8 that could cause this? http://forum.avast.com/index.php?topic=51232.0
Try .418 as its a recent release. If its appear again try their pre-release .447. Then if its appear again then feed back and they will see what they can do for you.
Remember to say up to date.