You need to recalibrate your screen manually.

N900 uses some kind of clever auto-calibration that observes trends of offset touches. If you use finger a lot, the actual touch point will be lower than link or what ever you aim. System can correct it automatically if this is the nearest clickable object. And if this happens most of the time it concludes that screen has to be calibrated by this offset. In remote desktop you have to use stylus and this is more accurate device.

I trained myself to touch bit higher than used to and screen calibration stays in place.