When I heard this I thought I just had to pass it on...
We had a new client a few months ago that had bought a brand new Dell laptop. He paid top dollar for it but after using it for a day it kept randomly going into standby mode by itself. Initially Dell blamed our software and said it was causing the problem... well it turns out...
They did all sorts up updating the bios etc and then all of a sudden the machine stopped going into standby mode by itself. Everything worked fine for two months, then all of a sudden last week it started to go into standby mode again randomly... after the client phoned Dell and had numerous people try and check the machine and run tests on it and tell him it was a third party software issue and that everything was fine with the machine... he was insistent and eventually got put through to someone in their support department who immediately asked him if he wears a magnetic wrist band - turns out he does.
So what was happening was that dell has a magnetic sensor that detects when the laptop case is closed which puts it into standby mode automatically - it is situated on the left hand side of the laptop out of the way - but since the client is left handed as he would type the magnetic wrist band would pass over this sensor magically putting the laptop into standby mode - of course whenever anyone else used the laptop it worked fine - so when they ran stress tests for two days they got no faults - it just so happened that he had removed the wrist band for the last two months, but last week had put it back on...
hows that!