having a similar issue to the overheating problem, but not quite the same. My 650 will become unresponsive and the screen will not turn back on if I don't use it for awhile. I'm fairly certain it's not a heat problem since it did it once while sitting on the table in my cold apartment. the normal 30 sec poweroff feature works fine, i just push the red button and the screen comes on, however when it sits for a bit longer, that stops working, I have checked the screen in the dark and under a light, it's not dimming it's completely off. pulling out the battery and putting it back in seems to be the only way back to normal. phone works fine as long as i'm pushing buttons. tried hard reset, newest cingular upgrade, battery is charged and phone is not even warm.