why wont my airport work???

i have a macbook pro, and it wont access my 2WIRE router for wireless use. like, it shows that im connected to the internet wirelessly, but it wont do anything. i did some research and everyone told me to buy an airport, so i did. but i dont know if i set it up wrong or something, because it shows up in my networks, but says i dont have any internet use from it either, just like with the 2WIRE. i know its not my internet card because the 2wire wireless works with all my other devices, but the airport doesnt work with any of them.