Rev. B iMac very slowly goes to sleep

[eXan]

So here's the problem (if it is a problem at all )

When I want to put my iMac (see sig) to sleep, it takes it around 20-30 to actually fall asleep. I noticed that it only happens when I used AirPort to connect to eMac/to the Internet. If the session was without use of AirPort, iMac goes to sleep amost immideatly, as it should be. Why is this happening?

Thanks