Posky Plane Issue

Hi gang!Some of my favorite planes are those from Posky. However I have an issue with them and FS-X. All planes (757-200, 767-200, 767-300ER and 737-800) are loaded into Simobjects/aircraft. 1. Only the 757-200 and 767-200 show up in the plan selector (not even a default generic icon for the others).2. When I select either of the planes that 'do' show up - they appear in the showcase window for a few seconds then - BLACK. The same thing happens if I select the plane and fly - the screen is black even though I can hear the engines running! A pan around will usually let me see the plane for a while then everything will go black again.Any ideas???Erik