Can’t get router to play nice with IP MA

Ok guys, here’s the deal. I got a branch office in Tucson, AZ connected to my office here in Phoenix. The connection is static 56k line with two Cisco 1602 routers. I have a Linux (RH6) server using IP Masquerading for Transparent Proxy (NAT). The Masq is set up to receive from all address and send to all addresses. (ipchains -A forward -i eth0 -j MASQ) The problem is, that from the routers, and ultimately the Tucson office, there is no route to the Internet. I can ping the private address for the Linux server, but not the public address. Nor can I ping any public address. The Linux server simply ignores packets from the router. Any ideas?