Problem with Airport not connecting

Hi, I'm a new Mac user. Just bought 2.6gb MBP but I'm having some network problems. I've looked through many forums and have never found a definite answer to this problem.

Router is Linksys WRT54G using WEP. It says I'm connected to the router, but I have no internet. If I connect through wired ethernet it works perfectly fine, but Airport is just not working?

Any suggestions would be helpful. Thanks!