Odd internet behavior. Any ideas?

My internet connection at school is odd. I can connect to chat programs (Trillian, gtalk) and I can connect to an mmorpg (like world of warcraft) but I can't use the internet (view webpages). This scenario happens frequently. There's also no way I've found that "fixes" it, aside from waiting it out.

Any ideas on how to fix this or what might be causing it?

[windows Xp, dell laptop w/ ethernet cable to connect to the network]