iPad 1 connect to router but no Internet

I just switched to xfinity. I have their router (10.0.0.1 gateway). I have also a linksys router off of that (192.168.1.1). I also have a airport express off the main router (ip of that ends up being 10.0.0.2). So total of three networks showing that I can connect to. I have an iMac, iPhone, iPhone, iPod touch that all can connect to any of those three wi Internet connection. My iPad (1st gen) will connect to the main router or airport express (10.0.0.-) but wIll not check complete in the iPad settings and no Internet. I can connect it to the linksys router (192.168.1.-) and get Internet just fine. I want to be able to connect to the main router, faster since it is located on the side of the house I am usually in. I have reset the iPad network settings many times as well as factory reset the routers many times. Any assistance would be great.

Having all three of those wireless routers within one home will invariably cause problems for your clients.

I would disable the wireless radio on the Comcast router (ISP-supplied wireless routers are notorious for being craptastic anyway). Then, I would setup the AirPort Express to act as a repeater for the Linksys router. In this way, you'll have one coherent wireless network.