My wife and I are both using free Evernote on Windows 7. I "shared" a notebook with my wife. When my wife clicked the link in the email invitation, she got the above error. With the help of Evernote support I was able to fix the problem. If you are having this problem, their fix may work for you. Create a new notebook. Move the contents of the old notebook (the one you tried unsuccessfully to share) into the new notebook. Sync. Delete the old notebook. Share the new notebook. As I said, it worked for me!