How can I troubleshoot the problem of playing World of Warcraft using the WIFI in a library?

I have never had this problem before. I always played World of Warcraft in the library over the summer. Ever since Cataclysm came out, it’s not letting me play in the library; it always says "Launcher cannot obtain patching information. Please check your internet configuration." I am connected to the library internet. I already have the patches for the game. I was able to play at my grandpa’s house, but not at the library. What should I do?