"Connection timeout" for new MacBook Pro

I received my new MacBook Pro this evening. I got home, got on my wifi network, and began transferring files from the old computer. After about four hours, my internet connection suddenly turned off. It was and is still working on the two other laptops and the two iPhones. The problem is only with the new machine. The router in question is an older Airport Express g router. If I try to connect to the network, it asks for my password again and then I always get a connection timeout. The computer periodically tries to reconnect; sometimes the wifi bars will go black for ten seconds and then I get an exclamation point and a message saying "Alert: No Internet Connection" when I click on the wifi indicator.

I decided to randomly open the disk utility, and I repaired permissions. Tons of stuff came up related to airport, and after repairing permissions, it immediately started working again! I started transferring music via home sharing, and I lost Internet after about ten minutes. Repairing permissions was not a fix the second time around.

Has anyone dealt with this? The fact that the Internet is working on all my other devices and the new computer connecting to the Internet at random makes me think there is a strange problem with the new computer.