I have an OKI ES9431 with 4 Trays (3+1). When I use the OKI Postscript Driver to print I can select trays 1-4 and print from them. When I use the Efi Fiery C9Server Driver (which prints better than the normal driver) I can only select tray 1 (it doesn't detect the 3 additional trays) and in any case when printing starts by selecting tray 1, it always asks me for paper from the rear MP Tray, so I can never print from the tray. Why? How do I solve this?