Apple Remote Desktop can't wake sleeping workstations

It appears that OS X clients cannot be accessed by the Remote Desktop admin workstation if they are asleep. Dave Ewers writes:

"The OS X clients here on our network all show as 'unavailable' once they have gone to sleep. The only fix is to visit the sleeping workstation and wake it manually. All our OS 9 behave properly. All of the affected Macs are iMacs running 10.1.3. All have the option to 'wake for administrative access' turned on in the energy saver preference panel."

Update: Steve Burling adds: "You can get around this problem without physically visiting the sleeping machine by using 'wakeonlan', a perl script available here. I use this script, run out of cron, to make sure that my Retrospect client machines are awake while Retrospect is trying to back them up. I also use it by hand if I'm trying to get at one of the machines to do administrative work.

Update: Brian Harriss adds: "There is also an OS X program called wake550 that uses the wakeonlan perl script to wake remote machines. Wake550 also allows you to store a list of machines you commonly wake up, so you don’t have to type in the MAC addresses every time you need to wake the remote computer."