I use FF 3.6.16 and don't see that with Avast 6.0.1.1000 and MalwarebytesPro 1.50.1.1000. Which versions are you using?
I have the latest versions of MBAM and AVAST but it happens since a few months, so it happened with AVAST 5 too

But ... I am sorry to say that ... but I uninstalled AVAST and I installed another antivirus, because there are too many problems with the new AVAST version, I can't search anything on my computer with the search tool ... it made firefox too slow ...
So it is my last message here

Bye
