Squeezebox Internet radio 'sputtering?

Your speed is more than adequate, but your connection is obviously breaking up somewhere in the chain. My first thought is that your router is the culprit, or possibly your ethernet cable. When you say you're using a Squeezebox/Duet combo, do you mean just the Duet, i.e. controller and receiver? Also, are you accessing the streams through Squeeznetwork or Squeezecenter?

I would suggest going over the Squeezbox forums and ask for help.

http://forums.slimdevices.com/

Thanks for helping out here.
I can exclude the Ethernet connection from the router as the 'trouble maker', because the sputtering also happens with the wireless connection. I am using a Duet with receiver. I have Squeezecenter open on my PC when I listen to Internet radio, but I frankly don't understand the function of Squeezecenter or Squeezenetwork in this ordeal. The forums you have pointed me to mention similar 'sputtering' problems but I cannot see a clear reason or remedy for my system yet. Why does 'speech' such as announcements ALWAYS break up/are scrambled?

Have you disabled the firewall?

Squeezecenter is selected when you want to use your computer as a Server, in other words, access your iTunes Library, it will also play internet radio stations, and your Computer (Server) has to be on all the time, also make sure that Squeezecenter is enabled to start automatically when you reboot your computer.

Squeezenetwork is used only for internet radio, and a computer is not necessary, you only need an internet connection.

You should not be having this problem with a wired Ethernet Connection, unless the cable is very long, like way over 100ft, as packets could sometimes get dropped. I agree with above comments; check your router, ethernet cable, and security settings on your router, sometimes routers think they're being attacked and then they usually just block further communications totally, as opposed to starting and stopping. It sounds like a buffering issue. Do you have kids at home who do a lot of online gaming as I've heard that could also steal some bandwith.

Good Luck!