So I went to boot my mac after leaving it off during the night and now nothing is displayed on my screen. The led on the monitor just blinks as if its getting no signal but the computer itself boots as I can open the cd tray, turn the volume up and down etc. I have a 2008 2x3ghz Quad core with the ati hd 2600 xt gpu. I'm assuming that the graphics card is at fault here? I've rebooted about 30 times, unplugged all cables etc and still noting. Can someone please offer some insight into what might be wrong? Thanks.