Wireless-G adapter not getting IP address

I've been using the Wireless-G to connect my XBox to a Linksys
wireless router for several months with no problems.

Now suddenly the Wireless-G is not getting an IP address, so it's not
connecting.

When I go to the XBox Network Settings, it shows that I'm connected to
our LAN, it has the proper SSID and Channel, it says "Connected" and
signal is "Very Strong."

But when I click "Connect" or try to access XBox Live, it times out.

I didn't change anything between the time it worked and when it
stopped working. It literally worked the other night, and the next
morning didn't.

What else can I check?