Coming from 11.0.1, I loaded a project into IDEA 11.0.2 Release Candidate. Somehow, the module I currently work on got severly corrupted: All Java packages that contain no child packages are shown as folders in the project explorer; the contained classes are not found when they're referenced in other files. I switched back to IDEA 11.0.1, but the problem persists. The module's .iml file didn't change. Other modules work properly, and the Ant build runs without problems. How can I revert the module to a usable state?