I've seen lockups on some machines, especially the e-machine amd64 laptops. To get it to boot properly, you'll need to disable pcmcia on those machines. This isn't an all encompassing problem, e-machines have all sorts of problems, even with XP64. I haven't nailed this down yet, it's something I just ran into a couple days ago, and it's a friend's machine.
Fedora locked up tight right at the keyboard selection stage, so we tossed in Knoppix (thanks Mr. Knopper!), and it locked up at the pcmcia autodetect. Just for gits and shiggles
, I disabled pcmcia (which unfortunately disables the networking on that laptop), and it booted like a charm. Of course, no networking is no fun, but if it's your system and you're familiar with Linux, you should be able to work on it from there. If it's a desktop or server, my guess is you're good to go.