Sorry about that. The alt-F# combinations switch between the text based virtual consoles, but once X is running, those keys are usually trapped by the display manager. So Ctrl-Alt-F# take their place.
If things are really stuck, you need to interrupt the boot process. A stock LILO installation waits for a couple of seconds before launching Linux, so you should have time to get to single user mode. When you get the boot prompt, type 'single' or 'linux single', then hit return. If all goes well, you'll end up in 'maintenance mode' (i.e. a root shell).