jargon.artrocity.com
New Hacker's Dictionary the Jargon File v 4.4.6
[IBM, prob. fr. slang belly up] Yet another synonym for ‘broken’ or ‘down’. Usually connotes a major failure. A system (hardware or software) which is down may be already being restarted before the failure is noticed, whereas one which is casters up is usually a good excuse to take the rest of the day off (as long as you're not responsible for fixing it).