I have been having problems with sometimes the computer turning on but getting no output from the graphics card. This seems to only happen about half the time it boots up, otherwise it appears normal. Sometimes it totally fails to wake up from sleep. I have been able to use Remote Desktop to gain access and have taken a screenshot of graphics card in about this mac when it has played up. Do any of you have any thoughts to help? It is a 2008 mac pro with 10.5.8. The graphics card is a ATI Radeon HD 2600.