Re-read the installation guide... Cache ownership, group membership, and modes are picky!
Cache should be owned by the CMOD instance owner, have the same primary group as the instance owner, and the main directory permission should be restrictive - rwx for the owner, and nothing for anyone else, a.k.a. "chmod 700". Never modify any of the subdirectories in the cache though. The modes are meaningful to CMOD, and store information on the state of data migration to secondary storage.
-JD.