An internal error occurred during: "Updating Maven Project". java.lang.NullPointerException

I solved mine by deleting the .settings folder and .project file in the project and then reimporting the project.

For me worked the answer I found on CodeRanch, by user Maneesh Godbole:

1. Close eclipse.
2. Navigate to your "workspace" folder
3. Ensure the setting on your OS to view hidden files is turned on
4. Identify and delete the .metadata directory
5. Restart eclipse
6. Import project

I've had the same problem in one of my modules.

Running "mvn eclipse:eclipse" in the console/cmd solved the problem for me.