It's not at all clear what you're trying to do. Are you trying to use File>Open in the editor on photos in the iphoto library? You can't do that because you should never, never poke around in the iphoto library from outside iphoto. That's the fastest way to corrupt your library and lose your photos. You have two options:
1. Either export the photo from iphoto, open the export in PSE and then import the edited photo back to iphoto as a new file, or
2. Set up PSE as your external editor in the iphoto preferences and send the photos from iphoto, then save, (not Save As) without changing the name or format of the image and iphoto will remember your last edits and the original. To set up PSE as external editor, note that the actual editor for PSE 10-11 is in Applications>Adobe Photoshop Elements (version number)>Support Files.
Hi Barbara, firstly thanks for your reply. I downloaded Elements last week and yes did file open and up came a menu? On it was iphoto album. I clicked on that and all my photos appeared. yesterday I took some photos in RAW and downloaded them to edit, and it wont allow me to access the album at all? It just says program error? Have I corrupted it?