I think the problem is with firefox itself. tedu@ wrote a post about this: http://www.tedunangst.com/flak/post/firefox-vs-rthreads
Since the code is so bloated, no one will ever waste time trying to fix all the issues. Just switch to some other browser, there's plenty of options. I'm using Links 2.12 on -stable and it works fine for my needs. But there's also Xombrero if you need javascript support.
