Making a boot floppy will fail because the kernel is to large to fit on a floppy disk. You could change the 'boot=' entry in /etc/lilo.conf to reference the floppy, and rerun /sbin/lilo (as root) to produce a floppy that contains the lilo bootstrap loader.
Whenever you run lilo, you need to make sure that there weren't any errors, because of there was, the information in the mbr won't be altered.
One alternative to produce an emergency boot floppy is to use:
This will produce a rescue image that you can burn to a cd disc. There will be a menu option to boot up from the hard drive.
Some other distro's have a mkbootdsk --iso option, but Mandrake's script doesn't have that option unfortunately.