problem implementing gamepad

i'm trying to make a game (based on kyatric's tutorizl on making z shooter gzme) for what i've tried until now everything is going wel except for one annoying thing :

i want to be able to control the game using a 360 gamepad so i looked in the doc and manage to implement it, well almost, i can move my "ship" unsing the left analog joystick and shoot using "A" but when i let go the left analog joystick, my ship is dragged on the top left corner of the screen

any idea on what i'm doing xrong ?

here's the capx

dl.dropboxusercontent.com/u/1434696/bad_gamepad.capx

thanks in advance

claude