I've encountered the same problem and here's how I fixed it.
The card you are using does not like DHCP for some reason. (I haven't figured out why) What you have to do is assign a static IP and it should pop right in. Next, I would highly recommend Buffalo wireless. My vendor put me on to them because I'm always looking for more inexpensive but reliable stuff. Boy howdy! These things are like $40 apiece and POWERFUL! Both the PCMCIA cards and the PCI cards. The Access Points are like $54 and just as reliable. I was using Proxim but these Buffalo dudes are putting them to shame thus far.
Well, sorry about the prattling, but there is my $.02 worh.
Take care. God bless you in all you do.
Lupe
308.254.5078
308.249.3755(cell)