the probleme is that when i'm inside a xfce environment i noticed that the mouse is a little bit creazy in fact when i point up it point down and vice versa the same thing for left and right even more i can't reach the margin of the desktop with the mouse
Touchscreen axes are inverted because you don't provide calibration data. There is package n900-configs that includes input device configuration file for Xorg, including calibration options amongst other things.