Add new segment button does not work in FF-27.x. As workaround in IE 11.x it does work.
In 8c4efab2eb13af59903275cb79734e9de3c22e5f: fixes #4833 fixes js error when adding new segment
If you go to Settings>Themes, and enble the Morpheus theme, does the button work afterwards?
@mattab: there was an js error (event not defined) in segmenteditor, which only occured in firefox. That should be fixed with the commit above.
Cheers Stefan, good find!