I hate to say it, but that sounds awfully like what happened to my reader. Here's my thread: https://www.mobileread.com/forums/sho...d.php?t=125946
I am currently waiting on a "suitable replacement", as it seems that a PRS-650 cannot be had for love or money. Or dire threats.
My advice would be to phone Sony ASAP and ask for a warranty replacement.
Good luck. (And don't bother fussing with your reader. Get on with your papers.)