I have this problem. Been having it for months. Really frustrating and annoyed that none of the updates have fixed it. Finally turned to the forum. Running 10.8.6 on mac. Whenever evernote has been open for a couple days, I can no longer view any notes. I see the thumbnails but I can't view or edit a note. Quitting evernote and restarting always fixes it....for a couple days. So basically have to restart evernote every time I want to use it !!!!