hostapd ip address conflict

[Onder, Hulusi TUR]

hi folks;
my hostapd configuration works fine however when i connect with the laptop to the hostap access point. the access point doesn't assign an IP address to the client.  the access point is connected to a network which has a DHCP server. and any commercial access points e.g. DWL-1100AP can connect to the network easily. i tried to assign static IP however it didn't work. i can see that the radius server is working fine. the logs are reviewed  and nothing seems wrong. 
my question is; can the IP address be only problem or is there another problem that you people have encountered similar to mine?
thanks