I have a problem with my PRS 600 with page turning using the buttons. Until recently I used the buttons almost exclusively for turning the pages. However it seems to have developed a rather annoying fault. Instead of turning just one page at a time it keeps turning until I press the opposing button and then it sometime stops but sometimes even goes into reverse and keeps turning in the opposite dorection. I now exclusively use the touch screen to turn a page. Has anyone come across this problem and if so is there a quick and easy fix?