That situation happened to me twice, while using AcidImage software. No amount of resets (hard, soft, etc.) could switch off the unit (my screen was white with several horizontal stripes of different colors). I had no recourse but to wait until the power ran down (until it powered off, automatically making a hard-reset).
The game you were playing caused a conflict with another software, and it is quite difficult to determine which one it is exactly (but it could be a new application you recently installed, or it could be that the game you were playing was recently installed and it is causing a conflict with one of your previous applications).
My advise is to avoid using that game. It will happen again when you use that program (not everytime, but it will just hit again when the conflict happens).
The AcidImage developer, and Palmone, could not find my problem because they could not simulate it unless they duplicate exactly all the softwares loaded in my unit, which was not possible.
Hope this helps.