Connects fine to WAP but can't get IP address via DHCP

OK, this used to work, now it doesn't. I'm stumped...

If I plug in my wireless PCMCIA NIC while I am wired to my LAN, it gets
assigned an IP address (I then have 2, 1 for the wired NIC and 1 for the
wireless). I can then disconnect from the wired LAN and have wireless home
internetworking, internet, etc..

HOWEVER, if I plug in the NIC when off the wired LAN I connect fine to my
WAP but my router does not assign me an IP address. In this scenario my
connection status shows packets being sent but zero received, and a
connection status of Very Good or Excellent.

I am using 64bit WEP, and confirmed I do not have either the Advanced
Networking XP Hotfix or the WPA XP Hotfix installed.

Any thoughts?

Thanks!