Bsod power_driver_state_failure

Hello,

I'm currently using 64 bit Vista as my OS, and I'm having two issues which may or may not be related.

Every now and then (at least a few times per day), my computer loses its connection to the internet. Nothing else that is connected through my router drops its connection - just the PC. Whenever this happens, we have to reboot the computer. During the shutdown sequence, we get a BSOD with the message "POWER_DRIVER_STATE_FAILURE". This message and screen stay locked in, and we have to cycle power to the computer to get it to restart (which always tells the computer was shut down improperly on reboot and asks if we'd like to go into safe mode).

Does anyone know why this may be happening? My files are attached.

Other information:

Vista x64
OS was originally installed on the system; is OEM
The computer was purchased about two years ago. The only modification made was the replacement of the graphics card and power supply. The OS has not been reinstalled.

Thanks!

I should also mention that for anti-virus, I run Kaspersky PURE.