You can try this:
Press Ctrl+Alt+t to open the Terminal.
Now type these commands:
This will remove the components for Unity:
sudo apt-get remove compizconfig-settings-manager
sudo apt-get remove compiz-fusion-plugins-extra
sudo apt-get remove compiz-plugins-extra
sudo apt-get purge compiz*
Now this will reinstall them:
sudo apt-get install unity-2d
sudo apt-get install ubuntu-desktop
sudo apt-get install ubuntu-desktop-2d
sudo apt-get install compizconfig-settings-manager
sudo apt-get install xserver-xgl
sudo apt-get install emerald
sudo apt-get install compiz-fusion-plugins-extra
sudo apt-get install git compiz-plugins-extra
sudo apt-get install compiz-plugins-extra
sudo apt-get install unity
Hope this helps you!