Intellij 9 release on Mac routinely corrupts the index of classes. This manifests itself with compilation errors claiming that classes X,Y,Z cannot be resolved. However, when you check, all the classes are in the right place. Also Intellij correctly compiles the individual class, and all the nice syntax highlighting, etc is working for these classes.
Go to Module settings and remove those directories by unchecking them as ‘Sources’. Click OK. Let Intellij reindex. Once, it’s finished, go back to Module Settings and add the directory(s) back into Source. Let Intellij re-index, and then do a rebuild.
If that quick fix doesn’t work, you may have to resort to the (very) long rebuild of your entire intellij cache: