I don't know. This message is not part of Panorama's code, so it must be generated by Apple's code. I just did a google search but it didn't turn up anything.
Panorama X files are in fact folders. However, they are a special kind of folder called a "package". It sounds like somehow your document lost the special sauce that allows a folder to be treated as a package instead of as an ordinary folder.
I am kind of surprised that it is ok to duplicate an untitled, unsaved document, but I just tried it and it seemed to work. The File>Duplicate command is entirely an Apple creation, there is no code written by ProVUE involved.