Weird Connection Issue. Please help.

So, I’m playing any online mode with my xbox connected over wifi and every time without fail when my roommate logs on to his windows partition (wired connection) and launches COD: Black Ops 2 through steam it causes me to drop my connection to xbox live.

Now I can kick him off if I reset my network settings and reconnect to my wireless again.

But that solution will only end in blood eventually.

Any thoughts?

He’s using a 2010 iMac running Windows 7
I’m using a slim xbox 360
Our internet provider is Shaw (Canada)
and our wireless router is a D-Link DIR-601