well i'm not surprised you are getting those errors, your repos are not synced with latest (the main problem being multimedia)
did you read this:
Update Pack 2 and Update Pack 3:
This release comes with Update Pack 2 and points to the “Linux Mint Debian Latest” repository as well as the Debian “Security” and “Multimedia” repositories.
Starting with Update Pack 3, “Security” and “Multimedia” become part of “Linux Mint Debian Latest”. When Update Pack 3 is made available, your sources will need to change and all of them will then point at Linux Mint. In the meantime, it is recommended not to apply updates coming from “Security” and “Multimedia”, as they might not be compatible with the packages in Update Pack 2.
or this viewtopic.php?f=185&t=82346
now, i think it's a bit to late, your system is updated, you got newer pkgs from debian.multimedia that are out of sync with the rest of your repos (mirrored by mint repos);
you can try to put the repos again in order (as per the last link i gave) and see if that solves the issue;
if it doesn't, you have 2 options:
- wait until UP4 and your repos will be fully synced;
- if you really need those apps now enable temporary the testing repo, update, install the apps you need and disable those repos again;
let us know if you need any help