menu launcher stopped working

There's a workaround for this problem posted by Doug McMahon here:

https://bugs.launchpad.net/unity/+bug/1057000/comments/37

From the comment:

To be a bit more verbose - for those looking for a tmp workaround till fixed - if no current /etc/X11/xorg.conf then create one with this in it

Section "Device"
  Identifier "NVIDIA GeForce"
  Driver "nvidia"
  Option "ConstrainCursor" "no"
EndSection

If there already is an xorg.conf with a device section then just add a line line in the section

Option ConstrainCursor" "no"

It's related to the new Nvidia 304.51 drivers, it's a known bug with no fix at the moment, the only way to get the panel behaviour back is to revert to the previous driver release version.