Hi, My Mac pro won't now start up. Nothing on the screen, fan running, but the two memory boards are flashing quickly and continuously - also a 2 red lights behind the memory is constantly on (looks like OT A and OT B). The only way to power down is to pull the power cable. I fear I may have shorted the graphics card with a bit of metal while changing a drive. I've tried powering down and holding the power button in for 15 sec - but no change. Any ideas on what I can do?