5-button mouse + firefox + mac?

when I switched to firefox 3 (in the beta testing days) I had a problem with my browser history buttons on my mac, they would not work! They worked in other browsers still, just in firefox it would give me this scroll courser called "autoscrolling".

This annoying feature is set here preferences->advanced->general. Also in about:config at general.autoscroll. I wish this could be set to one button; if middle-mouse did that --and nothing else-- I'd like that as a feature