Just found this from another forum. It worked for me.
¨So, if you're planning on editing a photo, copy the photo to a new folder (just to avoid making unchangeable edits to the original file). Then, open photoshop, on the menu bar select 'adobe photoshop elements 11 editor', and select preferences, and then general from the dropdown menu. A window will open. Here select "saving files". Change "On first save" to 'Save over current file'.
This allows you to save any edits you have made over the file you have open.
Its not a solution to the problem however. If you choose save as, the program will freeze once again. Also, though you can finally save files again, you cannot rename them, or change the file type within adobe photoshop - incredibly annoying!!!¨
It’s not a perfect solution by the looks of it (though you should only need to make the Preferences change once), but it does get around the problem when trying to ‘Save as’. Hopefully though there is an Adobe fix for the problem...