After updating to Maverick I was having issues with boot up where the screen would not turn on. The monitor shows no input signal and it would do it a few times after I manually turned the Mac Pro off by only holding down the power button. Then within the last few weeks it wouldn't come back on after a restart or if I shut down and then re-booted an hour later. Within the last week it seems to not boot up without pulling the power plug for at least 24 hours. I read somewhere on the Apple support that there was an issue with the Intel Mac Pros and not clearing the memory (or something like that) so I tried to check the video card and also pulled the power plug from the back of the Mac Pro. A day or so later I can plug it back in and then the screen would come up. I tried to read on the forums to see if there were similar problems with other people and I got the feeling that the 2008's had problems with the video cards. Maybe I am just seeing the problem now because we would only use it at night or on the weekends. Does anyone have any idea it is the video card or do I need to take it in to get checked? I don't want to have to get a new computer but it is getting frustrating. Then I tried to look for a replacement video card and apparently there are no new replacements for this model, but used cards or PC flashed cards that can work, but have limitations. Any help on what could be the problem would be greatly appreciated.