Can you please post your /etc/lilo.conf

For what it's worth, mine which boots SuSE and Knoppix is:

boot = /dev/hda
change-rules
reset
read-only
menu-scheme = Wg:kw:Wg:Wg
lba32
prompt
timeout = 80
message = /boot/message

image = /boot/vmlinuz
label = SuSE
root = /dev/hdc3
vga = 791
initrd = /boot/initrd
append = " hdb=ide-scsi"

image = /boot/vmlinuz.suse
label = failsafe
root = /dev/hdc3
vga = 791
initrd = /boot/initrd.suse
append = "ide=nodma apm=off acpi=off hdb=ide-scsi"
optional

image = /boot/memtest.bin
label = memtest86

image = /boot/vmlinuz-2.4.20-xfs
label=Debian
root = /dev/hda3
vga = 791
initrd=/boot/initrd.gz
append = "hdb=ide-scsi"

You might like to take a peek, edit yours as appropriate and run /sbin/lilo to write it. Do keep a back up of the old one, though!