Are your Tx batts fresh? Are you flying near power lines or metal poles, rails, or girders? Actually, any metal for that matter... Check for a broken antenna in the heli, loose plugs, and make sure your tail motor solder joints are tight and strong. Also, as a last resort, try replacing your tail motor. Try screwing in your Tx antenna. It may be loose. Ahh, so many possibilities..... Glitches have caused my Walkera DF#4 to go full-throttle and hit the ceiling twice (fortunately indoors both times and no damage) and once flipped the same heli completely upside-down[X(]

Man, that's annoying. I just broke my new blade grips and my hobby store ins't open til monday[&o] That's a total of $6 in repairs since I got this heli, which really ain't too bad... I suppose all my parts costs got covered with my DF#4...Something like $750 total in 3 years of flying on that heli[X(]