I'd be grateful for any advice on this issue. I have a HP Color LaserJet 3700 that works fine most of the time. However, when I use duplex printing, two papers are fed into the printer when the first pages are printed. When I have cleared the paper jam, the duplex printing continues without any problems. I have replaced the pick-up roller and the paper tray's separation pads, but that made no difference. Any help is appreciated.