OK I see. One other thing comes to mind. Some ESCs have a manual jumper plug to differentiate between (say) 2S or 3S, i.e. cell detection is not automatic. If that's true in your case, it may be expecting a higher voltage than your lipo has, and as soon as you run up the motor, it will cut off, thinking the battery is tired. I had this problem with a small Art-Tech ESC some time ago.

What is the name written on the ESC, and how many cells are you running?...Chris