Hi Lex,
I agree with Fabian. What you can try is:
1. Try to import the CommunityCommons in your project.
2. When you try to import a module that you already have, mendix will warn you that some libraries are repeating.
3. Make a note of this libraries that are duplicated and stop the import.
4. Manually delete all of these libraries from your userlib folder
5. Manually delete the module-package from the javascource folder.
6. Now import the CommunityCommons module again. You should no longer see any repeating libraries.
Hope this helps,
-Andrej
Most of the time this is caused by having multipe versions of the same java library in your /userlib folder. Try deleting all old ones.