Comment 5 for bug 373808

This is likely due to having some 32 bit libs already installed, which is perhaps a result of having a less than ideal yum multilib_policy:

http://www.redhat.com/archives/fedora-devel-list/2008-February/msg00168.html

Setting multilib_policy=best in /etc/yum.conf has resolved similar problems for me many times in the past.