I have just bought a used nook, and i have a problem with it. The thing is, sometime nook is working perfectly, but sometimes it seams like a there is something wrong with touchscreen. For example, i try to hit menu button, and when i press it, the star at the top lights. When i press home, it doesn't go to home screen, but hides the menu, as if i press at the top of the screen. The problem is there like half a time, then is normal. It's random.

My nook is rooted, but this problem was there before i rooted it.

What's wrong and how to fix it ?