I can't help, I am in the exact same situation as you. Except my dual 2.0Mhz is two years old. When it was new, it did it. And the "turn the option off that puts the harddrive to sleep when possible" thing helped. But after newest OS upgrade, the problem is back. C'mon Apple, we know the upcoming Intel machines are priority, but I think G5 users deserve some service still! Solve this bug.