LaTeX with MikTeX: Babel Error: Language definition file not found.

Typesetting a default LaTeX template using a freshly installed MikTeX + TeXworks environment ended up in the following error:

! Package babel Error: Language definition file main=ngerman.ldf not found.

I checked the MikTeX Package Manager and folder to be sure the installation was complete, but there was no error. Reinstalling the software wasn't successful, too. Browsing through the internet to find a solution, I found a comment, that  I have to update the MikTeX packages using the included updater.  And indeed that was fixing the problem. The template was simply using newer packages then MikTeX installed by default.

Get sure to run the MikTeX tools like the updater or package manager as admin to get proper results.