I've had good luck just installing it from the tar archive. You can download it from the Firefox page and run the installer.
After downloading the file just extract the files in it:
tar -zxvf firefox-1.0.4.installer.tar.gz
Then change to the firefox-installer directory that was created and run the install file:
I've installed mine in a directory in my home directory but you'll need to be root to install it any where else. The tar archive contains all the libs and whatnot needed to run so you won't have any conflict or dependency problems as with the rpm.