DSL, Cisco 675, Battlenet problems.

I have a Cisco 675, running my DSL through USWest (Quest). I don’t seem to be able to get incomming calls. Also, when gameing on the battlenet, I can not have people join a game that I start. Also, I have a friend that also has a DSL with the same company. We can not figure a configuration that will allow us to get into the same game. We are both annoyed. Is this a firewall problem. Is this 10.0.?.? DHCP issued TCP/IP issued address real? When we put the two computers on the same network, why do we have to change both of our TCP/IP addresses in order for the network to work. Even though I am an MCP, I know little about routers.