My DI524 is working just fine as an Access Point. I think I found a D-Link specific guide on setting up a router as an Access Point in one of the router manuals they post (DIR-635 maybe), but I can't find it again. Here is a great generic guide:
http://forum.portforward.com/YaBB.cgi?board=Knowledge;action=display;num =1133918703
(hope links to other forums are permissable here, I'm a newbie on this site, but I've been using DLink gear for years IF the link gets zapped, Google 'convert router to access point' and look for it there).
In short you have to connect the DI-624 by wire to your DIR-655. You disable the DHCP of the 624, give the 624 a static IP address. I put my 524 on a different channel, gave it a different SSID, and it runs great as a 'second network' on air that immediately kicks everything to the DIR-655. Now I connect N stuff to my N-net where it runs at 300, and my G stuff to my G-Net where runs at 54.
Now if someone could figure out how to convert a router into a Bridge (aka wireless client) we'd be smokin'

Jones