Time Capsule Problems

I just replaced my old TC with a brand new one under applecare. It is connected to my Motorola modem (I'm not at home right now, but i think it was called Surfboard or something?) and it is lit up green. I have 3 Airport Expresses, 2 of which are green and one of which is yellow (im not concerned with that one right now though). However, even though everything appears to be functioning correctly, I am not getting a wireless connection. I have the 4 bars on the airport, but no connection. When I connect my MBP to the TC via ethernet, the internet is fine. Does anyone know how to fix this? Thank you very much

Do you get an ip address to you laptop/computer?

Yes I do. The connection will work for about a half hour to hour and then just drop. I don't have a clue why.