dude, as someone who worked for a cable company and fielded these calls daily, i can tell you that the only option is (usually) to remove the source of interference or jimmy rig some kind of rf sheild and put it near your equipment (you can buy these but they're overpriced). switching companies has nothing to do with it. sort of like when you vaccuum and get all the lines. there are different types of interference. plixilating is actually different from a hum bar, which is what you would expect from rf interference. hum is when you get that rolling line up your screen. i would make a small wager that your cable wiring goes through some sort of house amp which is getting fucked with when you plug in the ballast. u-verse requires a lot of juice, so odds are good that they installed an amp to regulate the power (transmission not electricity). find out if you have an amp. if not there are other things we can look at.