my 8 month old iMAC 27" quad core machine recently started to "black out" Screen goes black for no reason and the only remedy is to hit the power button - usually twice. This will bring the system back to where it was, all open APPs etc. will be exactly where you left them. I also tested the speaker volume up/down keys to see if the "system" was still functioning during a screen black out. THe CPU etc. is still avtive as the speaker volume when maxed out will "beep" at you.
I called tech support - they had me do some special resets of power control and PRAM - no luck
I took the system into Apple store for Genius Bar appointment - 2 hours of running the mac in the store, of course it did not black out....however, they ran other diagnostics and ran a bunch of utilities, graphics etc. to max the RAM and CPU load, heating up the system but still nothing happened. they suggested I reistall the OS by doing a hard boot and holding down the command key to prompt me to re-install the OS from the "cloud". This did not solve the problem either.
I then took the system back to Apple and told them to fix it or replace it. They kept the system for 5 days, and replaced
item 661-5948 Board, Logic, 2.7GHZ, Quad Core i5
item 661-5967 card, video, AMD radeon HD 6770M, 512M
item 661-6615 LCD panel 27 inch with BLC
and labor: TOTAL COST $1183.32
This was all under the first year warranty so I did not have to pay for this out of pocket. If you look at the list of repairs, they effectively gutted my iMAC except for the HDD and enclosure. Ahhhhh at last I thought I would be back to a fully functional iMAC. Two days after getting home and just browsing the internet the blackouts started again.
Once the system blacks out the first time (which appears to be a completely random amount of time) it will then black out more frequently after hitting the power button.
It's time to call Apple again and demand a new system, wondering if the iMAC LCD crystal / video components are suffering from a manufacturing defect....as it seems the new components they replaced are suffering from the same issue.
APPLE - would appreciate you recognizing this problem and working on resolution.
Share holder and completely converted MAC power (family) users!!!!