OK, finally went to the Apple Store here after discussing again with Apple Care. The flicker problem is still occasional on mine. Unfortunately we didn't get this resolved - so I'd be really clear with Apple Care or the Store before going in so you don't waste your time like I did. The "Genius" and store manager said that they still didn't know exactly what the problem was. They think it's some combo of firmware and the graphics card. They could not fix at the store and would have to send in - with no assurance it would be fixed perfectly or that even a new one would not have the same problem. They said there would be a second firmware update "soon", and possibly a modified card. They didn't seem to be aware of a cable connection issue. They said I could leave the computer and have something back in 3-5 business days or wait. None of this sounded great - so I've decided to wait a bit longer - again, my flicker is very sporadic and not that bad. BTW - again, if I reboot it often goes away. There is also a keyboard shortcut to re-boot just the graphics.... option - control - eject and then click after it goes dark - in case this helps anyone.