DavidR
4
It isn’t that avast doesn’t work with firefox 6.0, but the WebRep.
However, your question is unrelated to this topic unless you are using the Server version of avast which I rather doubt. So this question should have been in the avast! Free/Pro/Suite forum http://forum.avast.com/index.php?board=2.0. A search of which for webrep and firefox 6 would find this.
http://forum.avast.com/index.php?topic=83248.msg678519#msg678519 or http://forum.avast.com/index.php?topic=83088.0