Wow, I almost forgot I posted this until I got my isolator in the mail the other day. Not sure this is of any use to anyone, but figured I'd post a follow up with my results.
I ended up reading about a
Viewsonics Ground Loop Isolator on another forum. Others had commented that it worked like a charm and did not interfere with digital cable capabilities. So, I figured I'd give it a shot since they were only $25 on ebay. Got it over the weekend and, viola, no scrolling horizontal bars! Worked like a charm. I don't have the bars any more, the low-level hum is gone from my audio, and my cable tv now looks like the video from my dvd player; spotless, and noise/line free.
Just thought I'd mention it in case anyone is experiencing the same problem. If so, this little thing is a gem.