wow, are you from the future? I have firefox 4.0 and its still in beta. You might have some fake software lol.
Now, assuming you have 4.0, I don't think firefox is the problem. I've been using 4.0 for months now, (or however long this beta has been out), and its been fine for me. I'm also using a mac, while you're using a PC, so there's a difference there. Try downloading Chrome or Opera and seeing if those work better. They are perfectly fine browsers. Your problem might lie in one of your add-ons. One might be conflicting with the viewing of this site.
I just upgraded to FF 5.0 and I cannot see the pieces. I also cannot post in this topic directly (had to write this in notepad and ctrl C/ctrl V)