24" iMac 2.16 - failing video and/or logic board?

[AllGold]

[quote StingMe]Seven passes of AHT and "No trouble found."
The extended tests? I'm guessing not because you would not have had time for seven passes of the extended test to run.

[StingMe]

Yeah, seven passes of the extended test - only have 1GB RAM installed and the hard drive is empty, if that makes a difference. Each pass was taking just under 5 minutes.

Running additional diagnostics and everything is passing so far. I don't get it.

[M>B>]

[quote incognegro]Not a G5 iMac, M>B>.
Contact them anyway, what have you got to lose!

[StingMe]

[quote M>B>]Contact them anyway, what have you got to lose!
I plan to take a trip to the Apple Store, since AFAIK the machine is out of the warranty/free phone support period. Of course, since this was an Apple Refurb, this may not actually be the case.

UPDATE:
Ok, this is ridiculous. All low-level hardware tests I've run have not shown any errors whatsoever...

I ran seven passes of extended testing via the Apple Hardware Test (version 3A113; from the iMac's original install discs) and no errors were reported.

I let the Apple Service Diagnostic (EFI; version 3S108) run for over eight hours last night (130+ loops) and guess what? That's right - no errors reported. When I tried to run the ASD (OS) tests I'd get a kernel panic at boot every single time, just as I do when I try to do any regular boot from any DVD (internal or external drive).

I am able to boot the iMac into SAFE MODE using a MacBook (OS X 10.5.2) in firewire target disc mode. The bazillion (ok, not quite that many) "stuck" pixels as described in a previous post above are observed but the system appears stable for the most part. I can cause a system freeze by running/testing the "Flurry" or "Computer Name" screensaver.

Does SAFE MODE disable Core Image/Quartz Extreme? Apple System Profiler reports that Quartz Extreme is not supported and I cannot launch Photo Booth or iMovie '08 because of this. I am also able to cause a system freeze by running an iPhoto slideshow (show runs ok, peppered with "stuck" pixels though) then hitting escape to exit it.

I've rebooted several times and can always boot (via the MacBook's drive) into SAFE MODE and can never boot in NORMAL MODE - no kernel panics, but the system freezes on a light blue screen with the cursor in the upper lefthand corner of the screen. I'm able to move the cursor but a copy of its icon is left in that corner as well. Ugh!

Well, I guess I'm out of ideas so I'll make an appointment to take the iMac back to the mothership for testing...anything I overlooked?

Thanks for all of the input so far!