User reports and I confirmed print both sides is greyed-out in microsoft word print dialog on iMac with Snow Leopard. I verified using the printer's control panel that duplex is enabled. Same user can print duplex from his MacBook with Tiger. Another user in the same lab can print duplex to this printer on his iMac with snow leopard. They are printing to the printer over our TCP/IP network to the JetDirect card in the printer.