Windows 7 suddenly fails to connect to 1 wireless network, connects fine to others

Hello!

I'm a software consultant and as such travel around to various client sites. At one site I'm working on now my computer now fails to connect to their wireless (it is one of those that says "Unsecured' but once you connect and launch a browser you are prompted for credentials.) I've been successfully connecting with this PC and this network for over a year, but for the past 2 weeks it fails everytime and when I try Troubleshooting it gives me the standard "Wireless Network Connection does not have a valid IP configuration" message.

My first thought when this began was that they had a hardware problem and that their router was failing to assign IP addresses. However, others sitting in the same cube area as me are able to connect to it successfully and I have not once succeeded in two weeks now. Also, I have no problems at all connecting to OTHER wireless networks (home, other clients, Starbucks, a wireless hotspot a co-worker set up here to unblock me the other day, etc.)

I have not found anything in searching online that helps me to determine how to troubleshoot this since it is only related to one single network.

Any ideas?