Just look for a download of 3.6.1.5......I also went back to 3.6 5 minutes after the auto update. (make sure to turn off auto update of firefox) I REALLY DON'T LIKE 4.poo. If I wanted a google chrome I would install it. Very sad for me I have been using firefox as my main browser in windows, mac and linux forever. But this 4.0 bla, I tried the beta and like everyone else said I DON'T LIKE IT. And they went google chrome anyway :(

This page will help you to disable automatic updates http://www.technipages.com/enabledisable-automatic-updates-in-firefox.html This page will provide steps regarding downgrade http://malektips.com/firefox_0039.html

Downloading Firefox 4 today caused both my Firefox and Chrome browsers to slow down markedly. So I un-installed Firefox, and now Chrome works just fine. I'll probably return to Firefox when it's running well and the add-ons I used are available. Bit of a pain though.

I uninstalled it and went back to 3.6 within 5 minutes, glad I had the install program sitting in my to reinstall backup, simply because they choose to do away with the save option on exiting when you have multiple tabs open. I love that option because I often have several tabs open which I'll need to come back too and with that gone I lost several pages that I had open. Now that's not a major problem but if they tossed that wonderful option in the name of "economy" or whatever I don't want to find out what other more important stuff got tossed.