I'm currently running 10.3.7 on a G5 Powermac. This problem was also evident on 10.3.6. The problem - The unit will not go to sleep on it's own when a network drive is mounted. Once the drive is unmounted, the unit will go to sleep in the prescribed time frame. For what it's worth, that network drive is on a Win-XP box.
I've been unable to find info. on this issue & didn't know if it was just the nature of the beast or something user configurable. Any & all assistance is most appreciated.