Audio stops

I bought a new Studio XPS 16 Notebook (running Windows 7) along with a Kensington SD400V USB Docking Station with VGA DVI and Ethernet.  Attached to the docking station (besides the notebook) is a monitor, printer and speakers.  The speakers are AC-powered (they include two average size 6" speakers plus a woofer).

Problem:  After a few minutes (of listening to either Internet Pandora Radio music, or iTunes, or other music), the sounds shuts off.  The software application that is running, whether iTunes or Pandora radio, then stops -- as it is apparently getting some signal from "somewhere" to pause or stop.  This is apparent from watching the iTunes display or the Pandora radio screen.  The sound does not start up again until I unlpug the sound jack from the Kensington docking station, wait a few seconds, listen for the sound to start coming from the notebook, and then plug the cord back in to the docking station.  At that point, the sound from the notebook will cut off and the sound from the external speakers will then kick in.  This may work for a few more minutes and then the sound will once again turn off.  The louder the sound, the sooner it will shut off -- which makes it appear as if it's a power (drain) issue.

One other note:  If I plug the speakers directly into the notebook, the sounds works forever.  So the problem is somehow connected to the Kensington docking station, or to the XPS 16 / Kensington relationship.

I purchased all of the items from Dell, including the Kensington docking station.  I spoke with Dell support about the issue.  Dell said it is a Kensington problem.  I spoke with Kensington support.  Kensington said it is a Dell problem.  After a lot of testing with both parties, updating software and drivers as each recommended, I finally convinced Kensington to send me a new docking station.  The same problem persists with the new one. 

Either this docking station is not made to handle this sound, or the notebook cannot handle the docking station, or Windows 7 cannot handle it.  I'm ready to throw all three out the window.