Homegroup visable but not connectable

I am running 4 win7 comps (3 - 64 bit, 1 - 32 bit)

Gateway laptop - 64 bit - Wireless n connected
E-machine - 64bit - Wireless n connected
MasterBedroom Desktop - 32 bit - Wireless n connected
Living Room HTPC - 64 bit - Hard Wired connected

These computers are connected to a wireless belkin n600 dual-band router. This router is set to access point mode (dhcp off, firewall is also off). No 5ghz freq is being used from this router. The belkin is behind a uverse 2wire modem/router (gateway). Dhcp is enabled along with firewall on the 2wire. It appears to be assigning ip's fine.

Wiring : Patch cable from 2wire lan port to modem port of belkin and patch cable from living room comp to a belkin lan port. Other 3 comps are wireless connected.

Here is my problem. I create a homegroup on the livingroom pc and all other comps say they are available to join and even see the homegroup created. But when attempting to join they eventually time out and give an error message saying they are unable to join. All other comps but the livingroom can create or join a homegroup to completion. Livingroom can not join a homegroup nor can other comps join its homegroup to completion. How do I get this livingroom comp to connect or be connectable?

I have synced all the clocks via internet clock sync. All pc names are different. Passwords are correct. All comps have ipv6 enabled. The livingrooms nic says "no network access" on ipv6 whereas the other comps nic's say "no internet access" on ipv6.
I am stuck. Please Help. Thank You.

No. They came with the routers. They are not reversed.