I've only tried doing ad-hoc mode, and it works just fine, so that this for what it's worth.
It is possible that the firmware in the card in your airport is sufficiently backlevel that there is a problem. You could take it out and reflash it in your PC. You should download and install the vxUtils (TCP utilities) for your ePods as well. This will let you query the ePods to find out what it thinks its own name and IP address are. If you are using DHCP and you get a valid IP address, then you can know that your card is talking to your airport. You can also use the ping utility in vxUtils to try to ping your airport. Next, I would try turning off encryption everywhere to see if that helps.
Regardless of those results, you can try running your PC and your ePods in ad-hoc (peer-to-peer) mode to see if they can see each other. The Client Manager utility on the PC comes with a cool "link test" that shows you all the cards your card can see, and lets you send test packets back and forth to make sure things are working at a hardware level.
Basically, I would suggest the standard rules-of-thumb for debugging problems like this. Start removing any possible complicating factor (AP mode, encryption, DHCP vs. simple static IP addresses, different firmware levels, etc) until you have success. Then start putting them back one at a time until you are where you want to be.
Finally, at least in ad-hoc mode, my little bar graph in the system tray always looks like it is searching, and if I bring up the little status window, it always says that there is no signal. And yet it works just fine. Never trust the computer to tell you the truth. 
-- j
