Why do you need to choose it? Lilo has a 'default' option.
Anyways. Rebooting is something it shouldn't do automatically.... Unless your default runlevel is 6. But then i'd do it later (nice thing to test btw - does that work?)
I take it you have a bootdisk (if not, get one - read the 'bootdisk howto' if you need to find one).
Then check all lilo-settings (use the lilo-howto), run lilo and try again.
If that doesn't work, maybe the kernel is faulty. Try rebuilding it (kernel-howto if you don't know how to do that (those howto's are useful thingies)). Remember to run lilo after that or it won't boot. That's all I can think of atm.
If that doesn't work, try and find all info available (error messages, motherboard/bios type, HD etc etc) and say what happened.
Or post it on usenet, I think those guys are smarter (well, the guru's there are).