Firefox 1.5: nothing works better than with the 1.0 I had on my Mac. Nothing I would notice.
But things are less stable.
And suddenly pdf files only wanted to open with the ‘default’ Acrobat reader after a Firefox download.
Normal OS X associations were fine, nothing in the Firefox preference pane, nothing in the about:config
I downloaded the Rc Default Apps system extension and it did not have anything set to Adobe Acrapobat. FINALLY installing a program from 2003 called Misfox did the trick. There I found the connecting in question. Changing it, and then launching firefox again did indeed fixed it. Convoluted, too convoluted, if you ask me.
this page helped eventually.