When I worked for one client way back when, they had a server that would go down for about 5 minutes every night, for no apparent reason, the thing would reboot. They could tell from the logs that it rebooted every morning...
Finally someone actually stayed and physically watched the server...
Cleaning lady was coming in every night, unplugging the machine, plugging in her vaccuum, vaccuuming the floor, and then plugging it back in.
Needless to say, they decided to invest in a dedicated server room after that was discovered. hahahah
Amusing...but have you seen this similar incident that was a bit more serious?