Apple has just issued a fix that is meant to address the flickering/tearing/blackout problem that is happening with many new (late 2009) iMac screens.
This fix is not without controversy of course, as Apple is deleting posts in their discussion forum that (at time of writing) has now grown to 100+ pages. Most deleted posts center around speculation as to what exactly this fix does to the iMac, most notably the theory that it de-clocks the video card to prevent it from overheating.
If this is true, it could mean that the current iMacs have a cooling problem with their integrated ATI video cards. De-clocking the card (limiting the video card speed to a lower rate) would certainly keep the card cooler and potentially prevent distortion issues such as flickering, etc., but at the cost of speedier graphics capabilities. If indeed this is what the Apple patch does, it represents a less-than-optimal solution, especially for those who rely on speedy graphics capabilities.
Time will tell if this solution works for now in lieu of a more permanent hardware fix, or if the patch does something else altogether. In the meantime I’ll be applying the fix to my Core i7 iMac tonight!
**Update: This “fix” did nothing for me other than lower the temperature of my video card. The flicker problem remains.