I have a 2007 mac pro connected to a 23 inch wacom screen. My computer has ran perfect for several months now, the other day I left to go to the store turning my screen off as usual, upon returning I turned my screen on and received a message saying no sync and sleep mode. I am guessing this means that the video card is not responding to the monitor. Please let me know what you think the problem may be and if it is the video card what card to upgrade I currently had the Radeon ATI x1900 in it. Thank you!!!!