A peculiar issue with streaming

I work from home, and my office does not have a TV.  As a result, I will often use my laptop to stream live news video (CNN, etc.) while I work on my desktop.

Invariably, my streaming will become extremely choppy -- stuttering, pixelating, stopping entirely, dropping audio, etc. 

In an attempt to isolate the issue, I opened speedtest.net in another browser tab.  Immediately upon beginning the speed test, the stream became much better.

Over the past 2 weeks, I have reproduced this result over a hundred times.  Unfortunately, this issue is so persistent that I have resorted to having speedtest.net open at all times, and hitting "test again" any time the stream breaks down.  I've had to run it over 40 times today alone.

This solution stinks for a whole host of reasons, including the unnecessary strain it puts on the network, and I'd really like to get to the bottom of it.

I ran Namebench and switched my DNS to Cox, which didn't help with this issue, but did seem to make browsing a bit snappier.  Several hard restarts of the modem and router have not solved the problem.

I have the Premier package, using the Cisco DPQ3212 routed through an Apple Time Machine 802.11n (3rd generation).  All machines are connected to the Time Machine via wifi.

Incidentally, this solution works whether the speedtest is run on the laptop or the desktop computer.

Thanks very much in advance for any help you can offer.