Today was the first flight test of my upgraded Easy Star with the ArduPilot installed. I encountered a few problems that will take some more tests to diagnose. Would appreciate any comments.Here is the setup:-Easy Star with the aileron conversion as documented in this RCgroups posting.-FMA Co-Pilot-Towerhobbies 72Mhz 8 channel RX and Tower Hobbies 6XM TX.-EM-406A GPS-ArduPilot with the latest code (22 Feb I think) set to RTL.Previously I tested the Easy Star with ailerons and the FMA Co-pilot and found the performance to be rock solid. The only addition to today's flight was the ArduPilot and GPS. Take off was uneventful and I waited until reaching about 200 feet with the plane flying directly away from me to switch on the Ardupilot. I encountered two problems that I believe are likely unrelated.Problem 1: Shortly after switching on the ArduPilot, the plane started flying erratically, the throttle and all control surfaces moving in an uncoordinated and erratic fashion. I switched the ArduPilot off and was able to recover the plane. A little more testing showed that he plane behaved similarly, even with the ArduPilot MUX switched off. The plane essentially behaved as if someone was on the same channel and/or general radio interference. There was only one other flier at the field (that I could see, its a big park) and they were on 2.4ghz.Possible Solution: Move the Ardupilot and GPS as far from the RX and ESC as possible. If that doesn't work, try another RX, possibly a Berg.Problem 2: During the brief intervals where I was not experiencing this interference, I switched on the ArduPilot. The throttle behaved as expected and maintained altitude. It seemed like the plane was turning towards the launch point, but so slowly that I had to switch off the ardupilot and bring it back manually or it would have flow out of visual range. Again I didn't get to test this much as the interference problem was popping up frequently.Possible Solution: Even though I have enlarged the rudder on the Easy Star, when the FMA Co-Pilot is on and I try to turn the plane with rudder only, it takes almost full rudder deflection to make a reasonable turn. I believe there is a setting in the ArduPilot code to turn up the gain on the rudder which may solve this problem.Would appreciate any comments if it looks like I missed something.