Firefox 6 Beta updated 7/8/2011 seems to be very stable hope Avast! WebRep is made compatible soon or by the time it becomes Firefox 6 general release. WebRep may work fine just needs to be shown as compatible. I used it and it seems to work with FF 6 beta.
This is going to be a problem as fast as FF is releasing versions. At this rate they will be on FF10 by the end of the year.