http://docs.info.apple.com/article.html?artnum=86523 New Info!.
As I said before, apple attempts to chock it up to stupid customers not knowing difference between fan noise and noise induced over firewire bus. Also, they attempt to chock it up to poor audio signal flow (grounding issues). ...We're not stupid, we know it's processor/disk related. And for christ's sake it's not 60 cycle hum.
***(edit) I should note that my issue is regarding FW digital/RF noise that the above author seems to have rectified w/ CHUD tools (did nothing for me) rather than the acoustical noise that blnkbnkr seems to be experiencing at present.
They ultimately say, if none of these troubleshooting suggestions resolve the issue, and you have a dual 1.8 -2.0 G5, (there's a limited run that are eligible) we're eligible for power supply replacement through an auth. apple service center. I called Comp USA here in chicago, the guy was supposed to be getting back to me about it, as it was the first he had heard of it, but no response as of now. I think I'll call and bug him today.
Interesting point is, as you'll see in my original post, at one point Digi sent me copied text from an old Apple press release that had since been deleted acknowlidging the issue. BUT, now, as you see at the bottom of that page it was modified 9/1/05. To add that "we'll replace if..." tag.