You should always be able to get back to your main vt...perhaps your X server is actually crashing your machine.
Start up your machine in single user mode to prevent it from attemption to start the X server (or any other periphery services) automatically at startup. Do this by passing the "single" argument to your kernel in the bootloader. From this point, you should at least be able to use your console to figure out what might be going wrong.
See here for more details: http://www.tldp.org/HOWTO/LILO.html