In Photoshop Elements 6.0, I can't save JPEG files as PSD files.?

I upgraded from Elements 4.0 to 6.0 and have not deleted 4.0. When I work in either Quickfix or Editor, I copy the file first that I'm working on, then edit/fix it, then try to save and, as recommended, save as PSD instead of JPEG. When I try to retrieve the edited file, I get the error message that looks like a torn photo in a frame, which shows up in the organizer. If I don't save to PSD, then there is no problem, the JPEG edited file is there. Any suggestions?