The script that starts firefox in SuSE looks at 'file /usr/lib/firefox/firefox-bin'
/usr/lib/firefox/firefox-bin: ELF 32-bit
LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.4, dynamically linked (uses shared libs), for GNU/Linux 2.6.4, stripped.
You might want to look at a library package or two and see if there are 64 and 32 bit versions.
rpm -ql libjpeg libjpeg-32bit
The two versions should install to separate directories.
I was looking at a Fedora Core install and comparing, but then I realized that I was looking at a 32 bit system. I hope you didn't read the possibly erroneous information I posted before editing.
This reference mentions SuSE and Red Hat 9 as being bi-arch distro's.
If you are looking at a distro that jumps through hoops like running 32bit apps in a chroot environment, I would avoid that distro.