I'm on Verizon and I've had this happen once on the 10/25 WM6.5 M2.5 EnergyROM, after installing/initializing KForTouchPro and while playing with FPSEce I think. Actually it may have been PocketSNES or PicoDrive, I don't remember exactly, but I'd blame KFTP before the emulator anyway.
It hasn't happened since, but as of now I haven't tried those cabs again either.
My phone does sometimes fail to respond when it goes into suspend while I have a (native PPC) game running. The hardware buttons on the face don't do anything (although this is probably due to the game having them hooked), but what's odd is the suspend button at the top doesn't bring it back to life.
If I plug my phone in the charging LED does operate though, so the phone doesn't seem to have completely crashed at that point.
