If you have a separate /boot partition (in part to deal with the BIOS limited range of boot sectors), and you upgrade to RedHat 5.2 from RedHat 5.1, then the installed will create the vmlinux and System.map symlinks in the /boot directory after unmounting the /boot partition, rather than in the /boot partition file.
The installer does not twiddle with things like that. The partitions are mounted before installing RPMS and are not unmounted until reboot.