Have you checked your internet connection? While you haven't changed your service, your service could have issues? More people have moved into your area, changes on the ISP side to lower costs, etc.
A good way to check this out is to try doing a VOIP test. You can use the following link: »myvoipspeed.visualware.com/serve ··· iad.html
Make sure you do this while you are noticing issues. Run the test. When it is finished, click on advanced, view text. Then post the text here and we can take a look at it.
Usually, choppy voice is related ISP issues and not the box. While the box may be bad, the most common issue is the ISP.