“The following packages have been kept back:” Why and how do I solve it?

according to an article on debian-administration.org,

If the dependencies have changed on one of the packages you have installed so that a new package must be installed to perform the upgrade then that will be listed as "kept-back".

That article says sudo apt-get dist-upgrade will force the installation of those newer packages.

Note:

dist-upgrade will install all pending updates, with their new dependencies. If for some reason, you don't want to do that, you should use apt-get install package-name dependency-package-nameinstead.

http://askubuntu.com/questions/601/the-following-packages-have-been-kept-back-why-and-how-do-i-solve-it