Can't connect to my wifi network when external monitor is connected

The computer is a very new Retina Macbook Pro. The monitor is an older Alienware/Benq 20" (3:4) LCD. I'm using a DVI to mini-displayport adaptor and plugging into the thunderbolt ports on the Macbook Pro. Router is a Belkin F5D8233 Wireless N router. As soon as I connect the monitor my connection to my wifi network times out and refuses to let me connect (every attempt just results in a "connection timed out" error). However, I was surprised to find that I could connect to my neighbor's network without any issue. Anybody have any idea what the issue could be?