This issue has been reported previously, and has been resovled by setting the said exception. I have observed it come and go myself before AdBlock updated to be compatible with FF3.5. I've had missing trophies, flags, parts of faces -- virtually any possible image in BB.
I have no idea how it does it, but all signs point to the fact that it somehow does... Go figure.
I see this thread:
(103286.11). A couple of users saying it fixed it, but I'm always skeptical of user reports with no sensible explanation (sorry, users). And it didn't have anything to do with the original reported issue of "no face", which was not addressed in that thread.