v715W ADF Jam

Just adopted a slightly used v715w and everything on it seems fine except the ADF. I insert an original document, hear the click confirming that it's been detected, press the "GO" button, the page starts entering the ADF slowly but steadily, and then jams. The top edge of the paper is hanging about half-way across the bar where it's supposed to be returned to the lower tray. It's hardly the end of the world; I can still make copies off the glass but the ADF would be particularly handy for multi-page copy and scan. Would really appreciate any ideas.