Local PCs Can't See Each Other After New Modem Install

I recently got ATT u-verse and the POS 2wire modem/router won't let my local computers connect. I can FTP into my PS3, but can't run a media server. Can't share files between computers & can't connect to my Directv receiver with Directv2PC Everything worked before the u-verse. tried changing firewall settings, but no luck. tried turning off the firewalls on the computers, no luck. all devices have internet connectivity and are connected to the same RG through either a wired or wireless connection. .tried hooking another routers WAN port to a LAN port on the u-verse modem, with and withouit a different subnet, with and without DHCP......