Zyxel router won't issue IP's through AP's

My Zyxel B-4000 gateway router will issue an IP through a wireless connection to a laptop, but I cannot get an IP issued through any of the Zyxel B-5000 AP's. I am able to ping all of the AP's and the router with a wireless connection through the router, and Netstumbler shows signal from all AP's. I'm puzzled, because the network had been working flawlessly. Any ideas???