Are you running FC5 then download the FC5 firefox 32-bit rpm and if you have the 64-bit firefox rpm installed remove it first, the updated firefox-1.5.0.7 rpm (and others) can be found here;
http://download.fedora.redhat.com/pu...pdates/5/i386/
I'm currently running the RHEL5Beta1 (updated) which is based on the FC6 work with the 32-bit firefox rpm package with plugins installed (BTW, I'm using the 32-bit firefox to post this message), here's the list (partial I think but close enough to get you close) use it as a reference to get the 32-bit FC5 equivalents;
aalib-1.4.0-5.fc5.rf.i386.rpm
AdobeReader_enu-7.0.8-1.i386.rpm
compat-glibc-2.3.4-2.26.i386.rpm
compat-libgcc-296-2.96-138.i386.rpm
compat-libstdc++-296-2.96-138.i386.rpm
compat-libstdc++-33-3.2.3-61.i386.rpm
firefox-1.5.0.7-7.fc6.i386.rpm
gnome-desktop-2.15.4-1.i386.rpm
gnome-keyring-0.5.1-1.1.i386.rpm
gnome-menus-2.15.4.1-1.i386.rpm
gnome-vfs2-2.15.3-7.i386.rpm
gnome-vfs2-devel-2.15.3-7.i386.rpm
jre-1.5.0_09-fcs.i586.rpm
mencoder-1.0-0.28.pre8.fc5.i386.rpm
mplayer-1.0-0.28.pre8.fc5.i386.rpm
mplayer-codecs-20060611-2.i386.rpm
mplayer-codecs-extra-20060611-2.i386.rpm
mplayerplug-in-3.31-1.el4.rf.i386.rpm
seamonkey-1.0.5-1.fc6.i386.rpm
thunderbird-1.5.0.7-4.fc6.i386.rpm
You don't need to download any package you already have installed, but you need the 64-bit counterparts for the libs (think compat and gnome rpms). You may not want to use yum for this, just download what you need into a common location and use rpm (as root or equivalent) to install after testing to make sure you have everything needed;
rpm -Uvh *.rpm --test
Remove the --test switch when all the requirements are satified to really install.