That might be the source of the problem. There were new unity packages installed and old replaced. I think that it's better to replace old configs.
Originally Posted by NikTh
Anyway the first thing that I would try is to reset unity with unity-tweak-tool.
If that didn't help then try reinstalling unity-scope-home.
sudo apt-get install unity-tweak-tool
Next in line of usual Dash is not working solutions are:
sudo apt-get install --reinstall unity-scope-home
rm ~/.cache/software-center -R
Then logout and login back.
rm -rf ~/.local/share/zeitgeist
Also you could look at the contents of your ~/.xsession-errors for some insight what's crashing.
Some people also used this: