unwatchable channels due to interruptions in signal

For over a year now, we have been experiencing heavy pixelation and signal interrutions but only on channels 810 (NECN) and 842 (CNN).  We get an error message when this happens that says "the problem is on our end.  We are trying to fix it".  It never seems to get resolved.  Why would this be happening?  Is there a work around for it?