I have a 2010 Mac Pro under AppleCare which has started behaving oddly when trying to put it to sleep from the keyboard and which is displaying a screen flicker on wakeup. The Mac Pro itself is the 2010 5.1, 3.33 6-core, 12Gb 1333MHz DDR3 and 5870 card. The boot SSD is an OCZ Vertex2 120Gb (firmware 1.32) and there is a Caviar Green 512Gb in slot 2 for Time Machine. It is connected directly to the Apple 27" Cinema Display running at native resolution and is on 10.6.8. The only peripherals are the Apple full size wired keyboard and my Wacom Intuos4 tablet. There is no mouse. The keyboard is connected through the ACD USB ports. The tablet is connected to the backplane usb ports. About a few weeks ago, it started misbehaving when I wanted it to go to sleep. Clicking Apple Menu - Sleep always works, every time. Using Cmd - Opt - Eject on the keyboard is where it (usually) misbehaves. On Cmd - Opt - Eject, the screen will blank but the MP itself will not click off. The fans stay running. About 4 seconds later the screen wakes up again. When it is in this state, pressing Cmd - Opt - Eject again will only repeat the screen blank - wake process. Choosing Apple Menu - Sleep will correctly put the machine into sleep. If I Shut Down the MP and restart it the keyboard correctly puts the MP into sleep providing I don't use the MP for anything else. At some point after browsing the web (Safari), using email or playing Warcraft or running the Curse Addon Updater the keyboard stops putting the machine to sleep again. The second issue is a screen flicker when waking from sleep. The display wakes up properly and shows the last state of the desktop but about 2 seconds after waking up there is a flicker on the lower 40% of the screen. A fully legible image of the top half of the screen is superimposed over the lower 40% very quickly then goes away. The superimposed image is not corrupted or garbled - it is an accurate copy of the top half of the screen, correct way round etc. it flashes once then goes away and does not return. It does this even after a shut down, immediate sleep and wake even if the machine is cold. There are no screen artifacts afterwards, no tearing, nothing. The display is completely stable afterwards. Even when I have been playing WoW and the 5870 fans have spun up, the behaviour is the same as when it is cold. Wake... display desktop, pause a second to two, one flicker, perfect screen. It didn't use to do this before the sleep problem above - the two issues have appeared at the same time. Now in the interest of clarity and honesty I should say I have removed the stock cooler from the 5870 several months ago and replaced it with the Arctic Cooler Accelero XTREME plus. Due to the fact I have used Arctic Silver thermal epoxy on the card's memory chips I cannot reattach the stock cooler. The card has behaved flawlessly since installation and there have never been any tearing or artifacts or crashes. In fact, the card and entire MP have behaved flawlessly as we would expect under normal use. I do not have a spare card or monitor to test it on as this is my only computer. My neighbour upstairs has a 24" ACD and MacBook (unknown generation) so we do have some scope for cross-testing. So... any hints on diagnosing the Sleep issue please? Do you ned to see processes running? Any resets I should try? I will be moving to Lion within a few days of release as the benefits for World of Warcraft graphics performance far outweigh any initial teething troubles using Lion. Cheers, Daniel.