Are you by any chance flying on 8 cells with the stock ESC and Fusion motor, and with the canopy on? A lot of folks have experienced glitching (followed by ESC meltdown) with that setup.

A Kyosho Atomic Force motor is a direct swap-in and won't kill your ESC if you want to run 8 cells. Pretty much any 17-19 turn 1 or 2 wind car motor will work fine, but the AF is $20 US from Tower Hobbies.