Error Content Could not perform database operation. An unknown error has occurred. ORA-02291: integrity constraint (BB_BB60.GROUP_USERS_FK2) violated - parent key not found For reference, the Error ID is 9095cb58-02da-4a42-9a93-f730004cfeb0. Wednesday, May 2, 2012 6:14:12 PM PDT This is what it says every time I try to sign up for my assignment.