I have tried several hard resets with no results..
My MP900C loses it's screen calibration settings.. after 2 or 3 on/off's I will have to reset the calibration.. with this problem it usually thinks the stylus is set about 1/4 inch to the left.
Sounds like a hardware problem, either collected dust/dirt under the edges of the screen or loose lcd ribbon cable, hence the screw tightening procedure....