Galaxy S3 Wifi no internet on Comcast/xfinity router

Brand new stock Samsung Galaxy S3 will connect to Comcast-provided wireless router (Arris brand), but cannot get out of local network - I can ping other devices on the network, and I can even browse the admin page of the router, but cannot get on the internet. Other devices work fine. I've tried turning off security. I don't seem to have the disconnect problems others have reported - the connection is consistent. Oddly, I don't see the S3 listed in the "connected devices". If I run ifconfig wlan0, it shows the IP address, netmask but no gateway. I can set a static IP, but I still am unable to get internet. I can connect to other wireless networks without problems. Any ideas? Yes, other devices can connect - couple of laptops, kindle, wife's phone, my old phone (both androids) and ipad..