Try updating from the terminal instead of a package manager. You will see the dependencies that are causing it to fail to load. For example, the following packages are Gimp dependencies:
If you notice it's hanging on
libglib2.0-0, then try
sudo apt-get install llbglib2.0-0. If it installs, try
sudo apt-get install gimp and note the failed dependencies and repeat the previous step replacing it with the new failed dep.
Hopefully someone knows a better way, but this is how I resolve some issues if using:
sudo apt-get install gimp --fix-missing, or
sudo apt-get -f install gimp doesn't work. Some of the dependencies will have their own dependencies that may cause them to fail as well. Just trace them down until you can install all dep's.