I installed a 780 GTX in my computer (ASUS P6T DH Deluxe, i7 Overclocked at 3800mhz). But when I start UDK or some games, the computer gives a black screen after a few minutes and shuts down (No errors or blue screens). I have re-installed Windows 7 and even tried out beta drivers 326.41 (So it probably isn't a software problem.) Could it be the PSU (Coolmaster 850W?) Or could the card itself broken?