BTW your hobby shop is a keeper. You are lucky to find such a good one. Stay with him, he seems like a great guy. He will be a big help to you later on as you progress in the hobby. I agree there is either interference or a radio problem. Ask around your club and see if someone else is having problems with that frequency. Another thing to try is set the plane down with the transmitter off and turn on the plane and watch for any jitters in the servo's. This could be a sign of interference. good luck with your problems.

Mark Shuman