I am using Unity on Ubuntu 12.04. For some time now, the Applications lens is completely empty when I open it. If I search for any applications from the Home or Applications lens, no results show up. I have tried killing and launching the Applications lens as suggested at Launchpad, but it did not work. How can I get the applications lens to work again?
4 Answers
In the terminal try
unity --reset
and reboot to see the changes.
As far as the mentioned bug is concerned ,it was affecting the unity-lens-applications-5.8.0-0ubuntu1 (precise)
package and current version stands at unity-lens-applications (5.12.0-0ubuntu1)
.
It also states that fix is released
so please update your system , if already up-to-date than ignore this.
I know this has been fixed for the OP, but I had the same problem and it wasn't solved with the suggestions above. In the end I fixed with:
rm -r ~/.cache/unity && unity --replace &
My software centre was also broken and that was fixed with:
rm -r ~/.cache/software-center
From other posts I think the two may be connected hence posting both solutions together here for future searchers.

- 51
You can also use the command
unity --replace
and you don't need to reboot (more convenient). This command restart both Unity and Compiz and clean all the GUI like if she was restarted.

- 703
I am not sure but I think at least one of the previous fixes changes unity settings, setting them to default settings. This may be necessary, but sometimes just a restart of unity has worked for me. From another askubuntu site I found that typing the following in a terminal will restart unity and recover my lenses:
unity &> /dev/null & disown

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unity --reset
and reboot. – atenz Aug 08 '12 at 18:15unity --reset
worked. Please post it as an answer so that I can accept it. – Aaron Hill Aug 08 '12 at 18:36