the evidence is that Apple themselves have pointed the finger at the video card. I have replaced my meory with high quality RAM and still get freezes. I have also tested the RAM for errors. It passed.
Actually, I don't recall seeing anything official from Apple pointing at the video card. There is, however, other evidence which suggests it:
- Many (but not all) of the freezes seem to happen when the video is doing something specific -- I myself have only seen freezes on mine when playing WoW in full screen mode. Entirely circumstantial, however.
- According to a pair of reports on Digitimes (
here and
here - but they're subscription only, so just google the links to find secondary reports...), back in the start of August, ATI had apparently slipped up a couple months back and let out some 20000-30000 HD2400 and HD2600 Pro cards into the Windows channel that had defective BIOSes into the channel. As near as I can tell from searching around, that's the *only* source of that info - there's nothing official from ATI. But I suspect this is the main source of the "it's the video card" rumors.
- Someone in posted on a board somewhere (in French) that an Apple Tech "fixed" his freezing problem by replacing the internal video board in his iMac. Not the most reliable report, but interesting, and more fuel for those rumors.
All of which is circumstantial evidence pointing to the video card being the problem, and if it is, it may require a bios update to fix (as implied by the Digitimes articles). That said, if that were the problem, I would expect that any iMac manufactured after early August to not show this problem at all, and I've seen at least one report at least to a machine apparently manufactured fairly recently which still has the issue. So either it's not the video card, or there's some other video card issue at work here.