Your home theater system has developed a "Ground Loop" which is caused by having more than one ground connection in the system. Most likely, your cable TV combined with the ground of the ButtKicker power amplifier power cord is causing interference in the audio system. Any other electronic device with a grounded power plug might cause the problem as well.
You can eliminate the problem in your system by adding a "RCA Ground Loop Isolator". Plug one end of the ground loop isolator into the RCA input on the back of the ButtKicker power amplifier and then plug the RCA cable coming from your A/V processor into the other end of the ground loop isolator.