When upgrading the FC3 kernel from a version prior to 2.6.11-5asl, it is necessary to upgrade the mkinitrd package first. Failing to do so will result in an unbootable system.
Updated mkinitrd packages can be downloaded here:
http://updates.aslab.com/kernel/binary/FC3/i386/mkinitrd-4.2.8-1.i386.rpm
http://updates.aslab.com/kernel/binary/FC3/i386/mkinitrd-4.2.8-1.x86_64.rpm