you can try rpmfusion.org given rpms or source rpms i had problems with my wifi (bcm4328) on fedora12, and best sollution I got is to use rpmfusion rpm's if I remember I installed broadcom-wl, kmod-wl-5.10.91.9.3-3.fc12.6.i586 and kmod-wl-5.10.91.9.3-3.fc12.6.i586 rpms
As far as I know, the EL5 repository of RPMFusion does not provide the kmod-wl (I'll be happy to be proved wrong!)