I was practicing tonight at medium volume and experienced a problem with my rig I had not had before. Whenever I would play a relatively hard note on the E around 4th, 5th or 6th fret, I would get a distorted sound that cut in and out. Kind of like buzz-buzz-buzz-buzz in rapid succession that only faded out once the note started to decay. I tried two different basses and different cables. I normally play through a couple of boxes, but went direct into the amp and got the same problem. I also tried one cab at a time and got the same result with each cab. When I play other notes (even a hard open E), it sounds fine. I run an SWR SM-500 head into two Berg 112s. Any Ideas?