@yayaba
I had a lot of issues with FF like not being able to drag the favicon to mail.app to send the url, and constant quitting and so on. Recently I did a system reinstall including a fresh FF, and FF is back to normal...
So if you really like using FF for certain features as I do then I can suggest a time consuming process that is worth trying...
Wait till your next system update, like Leopard for example but before loading Leopard, completely remove all traces of FF from your system, every bit. Then start afresh. Do screen grabs of your passwords and stuff and put all your bookmarks back in manually don't import them.
Sure this is a big pain in the bum, but if you don't have any luck and you like FF, it's worth it. I'm pretty happy with it now.