Re: System locks up on monitor power off....
I had a similar problem about 10 years ago with a firewire front panel extension addon and firewire devices connected would cause a hard freeze. Turned out to be a ground loop problem. You can isolate this by using those 3 prong to 2 prong power cord adapters on the computer and the TV, and/or try disconnecting other devices that are connected to the TV. Eliminating the ground prongs isn't going to hurt anything, it's just there as a chassis safety in case the phase wire touches the case of the device.