I have a D-Link 614+ and the 800AP access point setup in my apartment, with a G4 tower at the 614+, and a 12" PowerBook wirelessly connected. I was having problems connecting to file sharing if I was connected to the access point, but not if I was connected to the 614+ itself; there were no other problems.
I figured out that even though i had the tower connected via Ethernet to the 614+, it was being given two IP addresses: one for Ethernet, and one for AirPort. This didn't impact any other operations, but for some reason, it just wouldn't work conecting through the access point. I turned off AirPort in the tower, and the problem was solved. I'm sure this affects a very small number of people, but it was very frustrating and I didn't find any info about it on the web.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030822225543222