Hi, My Hero (T-Mobile G2) just shut itself down and refused to wake up. It had been sitting untouched on my desk with a nearly full battery charge. When I went to wake it up to make a call it refused - the screen stayed black despite trying all the buttons, holding down the power button etc. In the end I removed and reinserted the battery and that forced it to restart. It's been fine for the half hour since then - any ideas what might have happened?