It sounds like you had the same problem I had once. That's how it begins, you can only hear a small noise and it will work again if you hit the device. Eventually, it will not work altogether. This is not a software issue, the problem is that after 4 years or so pocket lint may accumulate inside the device causing the motor to stop spinning. You'd be surprised, I certainly was!! The solution is to disassemble your n900, find the small motor and clean/rip off the lint obstructing it from rotating. I'm sure this will fix your problem and you'll be doing yourself a favor for the futue.