Can't access internet at public library Wi-Fi

Here's my problem. I'm trying to connect to the internet at a public library with my laptop through Wi-Fi using Windows XP, which is supposed to be a non-secure open network. I haven't been able to access through IE or Firefox for a couple of months, even though Windows is telling me that I am connected. The network is supposed to not be secure, which windows and NetStumbler both are telling me the same thing. I have been able to connect at this hotspot before but recently, it will not allow access for me, even though I show connected. The libraian told me that some people can connect and some can't. Is there something I have not set up right on my laptop, or is it their network settings that causes this? I'm able to connect at other open hotspots. One other thing, library is running on channel 11 and network next to library is running on channel 11 also. Could this be the problem?