Hello Stteffann and welcome to Mint,
What's happening is that you must have added some PPA Repositories in mint 13 that are no longer valid in Mint 14 or Need to be unistalled and reinstalled for 14.
you can disable them by going to software Manager, clicking on the edit tab and software sources. then the click on the other tab and un-check the following ppa's
Then exit the manager and go to a terminal and type
- Code: Select all
sudo apt-get update
now see if you can update using update manager.