I had tracking enabled on maep,with nokia messaging running for push gmail, the built in media player for music, with occasional use of the camera plus the odd SMS. I stopped media player after a while, and later on when I stopped for a coffee I realised the n900 had switched itself off. It wa totally dead & unresponsive - it would not power on again until after I took out the battery - when I put it back in, the phone booted up fine again.