I assume that your /boot partition is properly formatted (i.e. ext2/ext3)
Boot a knoppix bootdisk, mount your partitions in the way you usually would, e.g.
Code:
# assuming you have only a root partition and boot partition
# mount root (/) partition
mount /dev/hdxy /mnt/hdxy
# mount boot partition in proper place:
mount /dev/hduv /mnt/hdxy/boot
chroot /mnt/hdxy
# find out what the kernel rpm is called
rpm -q kernel
rpm --reinstall kernel-foo.rpm
# (something like the above)
Repeat last two lines for the grub package. I think that's all that resides in /boot, so after doing a grub install from the grub shell (unless grub is still installed and properly set up), everything should be back to normal (sign out, unmount, take knoppix out and reboot).
HTH,
Samsara