If the device in question looks like the one posted above, it's almost definitely a hardware problem. And yes, heat could easily cause a connector to shift or come loose and allow for poor contact. Heat should never be ignored when it comes to computers. If you have a device that's overly warm or hot, find out why and fix it.

To the poster of the problem N900: Would you ignore your leg if it went numb if some random person on the street told you it was fine? Why not take a picture of what your device is actually doing. That may actually help you out instead of making you look like a douche for posting other peoples pictures, implying they're your own.