If a user has the preference "Prompt me when entering a blank edit summary" selected, VisualEditor's save dialog has to be closed and reopened to work. The "Save" button is greyed out even when an edit summary is entered.
- Enable Preferences>Editing>tick Prompt me when entering a blank edit summary
- Attempt to save a VE edit and the prompt for an edit summary comes up, with save not an option
- Enter an edit summary
- Save is still not an option
- Exit out of the dialog by clicking X and click save again
- You can now save your edit with an edit summary
Firefox 30 on Mac OS X Mavericks.