Installed a used flashed 7970 from e-bay (not from MacVideoCard). It booted up OK, but it started blinking after playing a high def video for a few minutes. I checked the system and noticed only two of the six memory modules were recognized putting the system down to just 4 GBs. I shut down and reseated the ram. When I try to power back up, I got a black screen and a blinking power light. After putting the 8800 back in, I still have a black screen, but also have the video card fan humming. Would appreciate any thoughts or recommendations.