eGalax touchscreen calibration

[robosphere]

hello everybody,

my touchscreen is working, but i have a little problem. in the middle of the screen the touch is very well calibrated. but when i touch the corners, the mouse position is on another position than i have touched. for example: if i touch in the upper right corner, the mouse position is about 1cm down and 1cm left. on the upper left corner, the mouse position is 1cm down and 1cm right. this is very strange. i have done video calibration so that the xbian will not fill the whole screen, but this should not be the solution?!

hope you can help.