If you run the Wireless card ALFA AWUS036H with the rtl8187 chipset out of the box on Backtrack 4 Final Release, you can experience problems with the SSID not being correct interpreted. Sometimes the clients only sees the SSID as empty squares (in windows unprintable characters). The weired SSID is also filling up the AP-list on the client.
Applying this patch to airbase-ng will solve that problem:
If you from a client are able to associate with a SoftAP (Airbase-ng) but you don't get an IP address I would suggest you to try turning on the WEP flag/key.
But not getting an IP from dhcpd could also of course be a configuration problem. For solving that question there are I'm sure other threads.