Deskbar keyboard navigation doesn't work and deadlocks

[mmlr]

When trying to navigate the Deskbar by keyboard, expanding the Applications and Preferences submenu doesn't work. When you try to open the menu by the left/right arrow keys, the menu item loses its selected state and doesn't expand a submenu. When you now focus another application (clicking on the desktop for example) the Menu will go away, the leave button becomes gray and the Deskbar doesn't update anymore.