So, I'm painfully new to aperture but I was under the impression that if I drag and drop a group of photos from one project to another, it would MOVE the photos to the new project (as described here: http://documentation.apple.com/en/aperture/usermanual/index.html#chapter=5%26sec tion=14%26tasks=true). When I do this, the images remain in the original project and it does get added to the second project (in an album under the new project). When I try to delete them from the original project, it also deletes them from both the original project and the new album in the new project. When I "Undo" the delete, it restores the photos to both the original project and the album under the new project.
The problem is you are dragging them into an Album not a project.
If you drag them into the project they will be moved. If you drag into an Album they remain in the original project as well as appearing the album. (in the album they are really pointers back to the originals in the project)