What regulator are you running? I almost learned the hard way a lesson at the NATS 2 weeks ago. While running a YS 1.70DZ CDI and the Jaccio regulator setup, the regulator would not handle the current draw of both the plane and the motor. Brett Wickizer had a similar experience last year. It works fine on the first flight, but on the second one, the regulator apparently got hot and stopped working for about 2-3 seconds, fortunately I was on a long climb and the engine died and on the way down the regulator came back to life so that I was able to land. When I landed it was VERY hot. I normally run Ed Alt's dual setup and it has been bullet proof, but in the borrowed airplane I was flying it had the Jaccio installed. We immediately pulled it out and put the Tech Aero setup back in and flew with no issues. I wouldn't think you would be drawing that much on the electric side unless you had a servo binding or something.

Did you have your failsafe setup to do anything in particular, so that you KNOW it was actually going into failsafe rather than just a momentary hold due to lack of power?