I would imagine that the card has lost it's address... ...if you're using Windows XP, in the bottom right hand corner you may find a small icon with two computers. You can just as easily go to start, control panels, network, then choose the wireless connection, and right-click, repair.
Your computer will then, assumingly, through DHCP get its correct addresses. From there you can go back to your registration page and continue normal use.
In DOS, I'm assuming that they tried to release and renew the IP address, but were unable to do so because your machine is set to default it's network connection to your Ethernet rather than the Wi-Fi.
-SF