My iMac has display problems and I've been told by Apple that the logic board will need replacing. Seems like I'm not alone with this problem either. Several people have reported the same problem (error code disp/13/2) from the hardware diagnostic. I wonder how many users have to have the same problem before Apple identifies it as a defect?

i saw your article and figured i'd add my own little story:
i bought my dual 1gig w/ gf4mx a few weeks ago and after about an hour total of use my computer started flashing blue noise all over the screen during a quake3 (1.31b4) game. when i quit out of quake, as soon it got back into the finder (os x.1.2) it crashed totally, clock didn't even tick and the screen was stuck with blue noise. i restarted and it crashed on startup while the screen flickered incessantly (during the gray period before it got to the blue mac os x start up screen). i was using a mitsubishi diamond plus 91 (crt) so i tried a 15" apple lcd and it did the same thing, crash on startup.
i ran apple hardware test (it did actually load correctly, though the blue noise continued) and it gave me a video ram error (disp/13/2 was the error code). so i pulled out the gf4mx and put in a pci rage 128 and it worked fine. i called apple tech support and (after telling me it wasn't covered under warrant because i was using "beta software") they told me to take in to the local service provider, so i did. fortunately, it was covered under warranty and they replaced the motherboard first, but it was still messing up, so they replaced the video card and it's worked fine ever since.
-jonathan y.