If you install different versions of the ubuntu packages, there could be chance that you get following error:

The following packages have unmet dependencies:

After some trial-and-errors, I found out that only the method in the following link works for my case:

http://stackoverflow.com/questions/26571326/how-do-i-resolve-the-following-packages-have-unmet-dependencies

sudo apt-get install aptitude
sudo aptitude install <package-name>