The batteries in my UPS (uninterruptible power supply) are dying, and the new batteries are on the way. Unfortunately, you can't ship batteries via airmail because they're considered hazardous cargo.
When the UPS batteries fail, it causes you to lose power for no reason. And my server is hooked up to that UPS. I might have to plug it directly into the wall until the new batteries get here...
It chose the worst possible time, too. I think it was sometime in the morning. And I don't get up that early these days.