Keep away from children...
I installed an ERP system into a small manufacturing company roughly a 3 hour journey from our office. Initially everything performed perfectly, but a few weeks later the customer complained of extremely sluggish performance. Dialling in (this was in the days of 33k modems - if you were lucky!) everything looked fine. All performing as expected. But the customer kept ringing back with the same complaint. Eventually I was dispatched to take a look on-site.
It didn't take long to find the problem; the server was running a very complicated screensaver that took up almost 100% of cpu time. Of course when I'd dialled in previously, the screensaver was disabled. Apparently the MD had let his young son play on the machine, and that was the result. Cost him a day of my time plus expenses.
It's one of the first things I check since then, but I've not come across it again since.
Biting the hand that feeds IT
