Haha, I never thought new computers would throw me more than older ones.

you see, this G5 originally came with an ADC card. And, on the G4s, when you replaced an ADC card with a PC card that had been flashed for Mac, you had to tape two connectors that were off-spec or the system wouldn't power on. Well, I figured it was the same in the G5... cue intermittent kernel panics and problems restoring from sleep. (Sounds like a power supply or ram issue, right?) Well it turns out the 6200 really doesn't like being run at 4x speed in an 8x slot... and this is how it shows it.

Apple fixed their AGP implementation in the G5, and I didn't bother to look it up. :O

I pulled the tape, and now the system works wonderfully.