my psp's 'O' button went broken a few days ago. after i took it apart for fun. it keeps on sending message to the mobo that its being pressed. so literally, my 'O' button cant be depressed. i took it apart and it depressed. tried pressing it with my nail and noticed that the pressure point on the printed pad for it is no longer at the center of the designated place. it was on the outer side and just placing the button on the pad presses the 'O' button.
at first, i was thinking about cutting the rubber padding under the 'O' button so only the center of it touches the printed pad. that is obviously stupid of me.
so instead, i slid my small flat screwdriver between the 2 plastic piece of the pad to loosen it, and sticks them back together. and now it works.
so, if your psp is having a ghost hand pushing down on the button, chances are there are either something stuck under the faceplate, or the printed pad is like my psp's condition.
hope this helps someone out there.