So I had a striaghtforward single module java project working fine with Intellij Jetbrainz 12.0.1 no problem.

Then today it showed any reference to a class in an external jar in red as if it couldnt be found, although Build/Rebuild Project still worked without any errors.

I fiddled around with the dependencies, recreated the project from scratch, and then upgraded to 12.0.2 but still no improvement.

I recreated from scratch again

I have all my external jars in a single folder, and I add that folder to Modules/Dependencies

Without adding it build fails, if i add it the build is fine, but I still get every reference to these classes marked as red

Is something corrupt, how would I reset my default settings