Firefox 4 requires an Intel Mac. If you are still interested in Firefox 4, you can try http://www.floodgap.com/software/tenfourfox/ but that is not created or supported by Mozilla. If you want to go back to 3.6, you can download it here http://releases.mozilla.org/pub/mozilla.org/firefox/releases/3.6.16/mac/en-US/

I have the same problem! I've tried to fix it and in the process I've eliminated all firefox. Now all I have is safari!

Thanks, this is what I expected. I did look carefully thru the download site for a notice on compatibility with PPC-based Macs, and did not find any. I'd suggest adding this for other users (unless I missed it, but then it is not obvious enough). Richard

Thanks for the link, a heads up on the requirements would have just saved me 20 minutes of my life

http://www.mozilla.com/en-US/firefox/4.0/system-requirements/