Cool, so everything seems good there. Now which router do you have? Have you tried locking the network card speed down to 100mbps/full, 100mbps/half, 10mbps/full, and 10mbps/half?
I'm not sure this will work but it will narrow things down a bit. Also let's not worry about DHCP, let the router lease the IP address out for now. Let's assign the server 10.0.0.10, maybe there are some restrictions on the router??? I don't know but i'm just trying to see where the problem is coming from.