http://www.upubuntu.com/2013/05/how-to-fix-broken-packages-using.html
If you cannot install new packages using the terminal under Ubuntu 13.04/12.10 or older and you receive this type of error:
(...) You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies: (...)
You may try these various types of solutions that may help you repair your package database:
Tip 1
Via the terminal, enter this command to fix broken packages:
sudo apt-get --fix-broken install
Tip 2
If the above command didn't help, try these ones:
sudo rm /var/lib/apt/lists/* -vf
sudo apt-get update
Tip 3
You may also try these commands:
sudo apt-get clean
sudo apt-get autoclean
sudo apt-get autoremove
Tip 4
Another useful commands:
sudo dpkg --configure -a
sudo apt-get update
Tip 5
Open Ubuntu Software Center and if prompted to repair broken packages, click simply the repair button.