Sanyo green & magenta bars problem.

Hi hdtv group,

      I hope someone can help me.  I bought a new Sanyo 50" Plasma HDTV 3 
weeks ago.  When the cable people installed my hdtv, I began to see a
green 
bar & a megenta bar moving up the screen.  The cable man was here again 
today and gave me a new hdtv box and this afternoon the problem came back.

Analog signals are fine but everything coming from this box has the bars. 
When I disconnect the vidio cables from the new box, the bars go away.  I 
don't get it!  Does the problem have something to do with how this TV is 
handling the digital signals?  At times the bars are dispursed and don't 
seem to affect the picture and sometimes the bars shrink to about 2" wide 
and do affect the picture.  Should I return the TV or what?

                                                                          
  
                                                                          
  
         Thanks / Ed