On our pure scsi systems, when we updated our kernel's with the kernel-2.2.5-22 rpms, rpm failed to update lilo.conf to reflect the new kernel image as well as failed to create a new initrd. Rpm also deleted the old kernel image, which left lilo pointing to a kernel image which no longer existed.
(*almost forgot*) It also left the initrd entry in lilo.conf pointing to the old /boot/initrd-2.2.5-15.img, which will not work with the 2.2.5-15 kernel.