When I launch alacarte through the menu system the cursor briefly changes, but I don't get the app. When I try it from the command line I get this:
~> alacarte
Traceback (most recent call last):
  File "/usr/bin/alacarte", line 36, in <module>
  File "/usr/bin/alacarte", line 32, in main
    app = MainWindow(datadir, version)
  File "/usr/lib/python2.7/site-packages/Alacarte/MainWindow.py", line 44, in __init__
    self.editor = MenuEditor()
  File "/usr/lib/python2.7/site-packages/Alacarte/MenuEditor.py", line 51, in __init__
    self.applications = Menu(os.environ['XDG_MENU_PREFIX'] + 'applications.menu')
  File "/usr/lib/python2.7/UserDict.py", line 23, in __getitem__
    raise KeyError(key)
Any idea what I can look at to fix it?