Mine did this once, and I discovered my leather cover, which has a plastic rim that grabs the Playbook, included an external power button that was forever pressing down on the Playbook's power button. Once, I snipped the column of plastic that was pressing the power button, I never had the problem again. Is it possible that you have something pressing on one of the buttons?
unresponsive=screen keyboard and any interaction is troublesome Erratic=press one letter and another appeared; click on a pic and something different happens