I recently upgraded to WordPress 3.9.1 and now the "Insert/Edit" link button in the visual editor does not work when adding or editing a post.
Does anyone have any ideas of what it can be?
I had the same problem. I solved it by creating the link in a Word Processor document (Pages in my case) and then copy and paste into Wordpress. I had to edit the HTML text to open the webpage up in a separate window.
All working correctly now.