My dads customly built PC don't work when connected to a monitor. I put together my dads new PC and when I plugged it all in, the monitor power button was orange which meant it's on standby until I switch the PC on and it won't show a screen. I then Re-inserted his graphic card then I tested in through my monitor and it had a signal and had a screen but then when I shut down and started back up, my power button was blinking and telling me that my monitor can't detect anything? Short help: Dads monitor doesn't show a screen, other times he has a screen. It worked in mine a minute ago and now there's no screen. I think it's a graphic card problem. He has a Sapphire 3870 XT.