What's the distance between the router and mobo?
Have you tried rebooting your router?
How many other wifi devices are connected to it?
Can you connect if the encryption is disabled?
It's about 25-30 feet away through two walls. No other devices (laptops, iPad, etc) have any difficulty connecting to it. At any given time there are between two and four other devices connected to it, but it seems to make no difference how many are connected at any given time.
I have rebooted it several times.
I have changed the original encryption (WPA2) to WEP, and also turned encryption off entirely. I changed the wireless mode from mixed to G-only. None of this seems to make any difference. I also made the router use the same channel that my phone's wifi hotspot uses, but that didn't help either.
Since it seems like it's a specific issue between this card and my particular router, I think I might pull out my old WRT54G v6 and see if it makes any difference.
Any other ideas are welcome.