Are there any guides on how to debug a full machine lock-up on GNU/Linux?
I'm sure there are, but first, you should confirm that the machine is
fully locked up. you may have a process or to that are out of control
and have locked you out of the keyboard, but not necessarily the whole
machine. Ideally, if you have another machine, you could try to ssh in
to the locked box. sometimes this works as you can get into the
machine and using top and other tools, see what is causing trouble and
kill it to regain direct control of the machine.