When a client connects to the switch directly via ethernet we have no problems getting an IP. When connected to wirelessly we can not get a DHCP address, but if I set the IP to static, I then have no problems. Please note that the DHCP server being used is on the PIX firewall, and not the 2106 Controller.
The only place I see where this could be an issue is the Access Control List for the WLC2106. But this should not be the case as the current policy at the moment is to permit anything and everything.