When connected to an airport router, my Macbook Pro cannot view certain websites

Hello,

When my Macbook Pro is connected to my Airport router, I get a "No data received" error when trying to access Youtube, Wikipedia, and a hand-full of other websites. When I try these websites on another browser, I get other errors as well (Firefox: "Your browser was reset." Safari: Nothing happens, blank screen is displayed.) When I am connected to another wireless network, I don't have any problems with these websites. Any advice for what I can try to resolve this?