I have LinuxMint 17.1 VM under Win7.  This morning, when I ran Mint, a message popped up and said that there were updates via Update Manager.

I’m not an expert on Linux by any means, but figured I’d better install them, about 400MB worth. Guess which program didn’t update? Yep,  Update Manager. It was suppose to be the latest version 4.8.4. 

I opened up a terminal window and this did the job via command line:

sudo apt-get update        # Fetches the list of available updates
sudo apt-get upgrade       # Strictly upgrades the current packages
sudo apt-get dist-upgrade  # Installs updates (new ones)

Remember that you need to enter your super-secret password after each sudo command. I also used the default for any install errors.