Problem with MN-700 for playing Starcraft

My desktop and notebook is now connected in MN-700 and the
desktop uses ordinary wired network card and the notebook
uses MN-720 for wireless network card(however notebook has
a wired port).

The problem is that I and my friend tried to play
Starcraft in Battle.net in same time using my desktop and
notebook, but we couldn't play together in the same game.
When we get into same game, the game speed was getting
very very slow. I ve tried to use IP forwarding and DMZ
options in the Basement Station Setup, but it wouldn't
work.

By the way, my previous device had no problem with this
issue at all. This problem occurred when I changed my
device to MN-700.

And I am using COX cable network in Fairfax, VA. However,
I don't think this is because of cable network. Because, I
tried my previous routing device when MN-700 couldn't
support Starcraft well, and the old one was worked well
with Starcraft.

So someone help me.