The 990 and 1070 differ on this one a bit. Both units will transcode composite and s-video inputs to component output (including any OSD menu or information pop-ups generated by the unit on those input signals), so that you can access the OSD menu from the component output. The 990 will do one additional thing, however: on component inputs, it will replace the incoming signal with a black background and display the OSD menu on that background. One kicker with any of these scenarios - both units handle transcoding to component by producing a 480i signal, and the 990's "black screen" OSD menu on component inputs is also produced at 480i. This was actually my first suspicion (back in the second post of this thread), but I didn't pursue it far enough: if your display device won't accept 480i component inputs, it won't be able to display either the transcoded composite and s-video signals or the "black screen" OSD menu.

Here's a test to confirm whether your projector can accept 480i: set your Denon to interlaced (so that it produces a 480i output) and see if you can get a picture on your projector. You can actually leave the video switching through the 990, since it won't change anything about the signal anyway.

If your projector does in fact refuse to display 480i, you may want to consider the small TV monitor that others with projectors have used. That'll let you get into the 990's menus and even preview sources (assuming you run some composite cables from those sources so the composite monitor output has something to work with).