Frequently while responding to a text (via Handcent) or browsing the web (via Opera) - the screen will jump instantly up to the top or start scrolling up to the top on its own. Putting my thumb on the trackpad stops it until I release. However I can scroll back down to where I was but as soon as I let go it scrolls back up again. I have no 3rd party apps that would cause this and there is no dirt, scratches or foreign contaminant on the trackpad that should cause this behavior. Any ideas?