could you temporarely move your pc so that you can plug directly into the bt master. If this cures the problem you know it is something to do with your extension wiring. Try the simple things first. If you do move to the master and it is one of the latest type with the 2 sections you can undo the 2 fixing screws and remove the bottom section allowing you to plug into the line itself without any of the extensions connected. Also try different filters as they vary greatly.