Weird picture in picture with on demand

Occasionally, when selecting an On Demand program to watch, it will start playing in a small box in the upper right hand corner of my television screen, but with no volume.  If I exit out of On Demand and go to regular live tv, a dvr recording, or try On Demand again, the picture in picture is still there, still with no volume, and the only thing that makes it go away is doing a set top box reset, which I can't do right now because my dvr is recording another program.

Thing is, neither my Cox set top box, nor my Sharp Aquos television, support picture in picture at all.  Don't know why this is happening, but it's frustrating.