Images Disappear When Album Moved

I use Aperture 3.4.3 in a managed approach for my files. When I move an album from one project to another, or to another folder, the images disappear. However, the proper file count shows up to the right of the album name in the Inspector. So the album counts the files, but does not show them. I have no filters on (Library search window says "Show All Files").

I typically import to a 'working' project, then move finished photos to their final project. I never had this problem until I think v 3.3. Now it seems to happen routinely. Even after I move the masters from my working project to the same project where the album is now located, the images still don't show up in it, though I see them in the project itself. If I then drag them into the album again, the album count doubles, but images still don't show up. If I recreate the album photos show up as usual.

Any clue what is going on?

Thanks, Steve