It seems to be an actual physical problem (if it is a problem at all.) The screen used to feel as hard as the top screen when touched with the stylus however now it feels almost spongy - well, at least softer. It feels like there is a layer of thick plastic, that wasn't there before, over the touch screen. I will, however, try calibrating it.
It doesn't make much difference, except that I have to touch the screen slightly harder to get a response - the screen now feels more soft and flexible, as if there was some sort of cover over it.
Thanks for the help, though! Any more ideas?