If you are updating your system via the terminal and you have updates that won't install you need to use another command.
sudo apt-get upgrade will not install updates that will install other new packages as dependencies or package removal for the installation of other packages: new kernels, new GRUB versions, etc will not be installed with it because they will do so.
apt-get upgrade will only update packages currently installed in the system.
For updating packages that do changes to your system use either the Update Manager or in a terminal the command
sudo apt-get dist-upgrade.