are you seeing this problem before or after lilo loads? if its before lilo is messed up but if its after then your /etc/lilo.conf file is probably messed up. Either way it would probably be easier to go into a live cd and look at your lilo.conf.
Here is a sample from my lilo.conf file:
# Linux bootable partition config begins
image = /boot/vmlinuz
root = /dev/hda1
label = linux
# Linux bootable partition config ends
The 2nd cd on the slackware set is also a recovery disc, now I don't know how to use it but you could probably use it to mount the harddrive and then look at the file and re-run lilo.