Airport Express needs to be restarted every 10 mins

Ok so here is what I am working with. I have a Mac Book running 10.5.8 and I have a Apple Airport Express running 7.4 which is the newest install. I am trying to get steady wireless access. My airport goes out every 10 mins or so and has to be restarted either manually or from the airport utility. It will then work for about 10 mins but then will go out again. The airport utility and the airport express both have green lights and say that everything is fine. But the browser says that I don't have internet. I am not sure what the problem is. I have tried changing channels. But that has not helped. Any ideas on why this is happening would be greatly appreciated.

Thanks
April

more details on the internet set up

Ethernet
Using DHCP
IP address 72.130.184.69
DNS server 209.18.47.61, 209.18.47.61
Sharing a public IP address

I hope that is your computer to router IP and not your actual internet one. If it is remove it ASAP. If its the one that connects your router to your computer then it looks invalid. Normally it would be something like 192.168.0.2. For me personally if it looks like that it means another computer is using the 192.168.0.2 IP causing it to get the internet and not me.

I have had trouble in the past with routers that have an automatic timeout of 10 minutes. However I have no experience with Airport Express.