Ubuntu 14.04 - No Unity in user account, but in guest account

Solution 1:

Open the terminal using (ctrl+alt+T), and try to reset compiz and unity by:

sudo apt-get install dconf-tools    
dconf reset -f /org/compiz/       
unity-reset
setsid unity

If you are still facing it, then open terminal again and reinstall desktop and unity

sudo apt-get update
sudo apt-get install --reinstall ubuntu-desktop
sudo apt-get install unity

Solution 2:

It's probably something in your $HOME. You may want to temporarily move whatever contents you wish to save to somewhere else, remove the remaining files in $HOME, and copy the files in /etc/skel to $HOME. Doing so would eliminate your personal settings, but since you just switched from Mint I'm assuming it doesn't matter.