I've three DNS 323s, bought at different times, identical disks, firmware and settings in each. One refused to go to sleep, the others were ok. Last night, updated to 1.07, no change. Tried various other things as recommended on the thread, no luck. The NAS was set to sleep at 10 minutes. Changed the setting to 15 minutes and it worked!!! Don't know why, but maybe it'll help someone.