You are running out of slots in the enqueue resource table (seen via V$RESOURCE) because you are not releasing the locks on those resources. Locks obtained with DBMS_LOCK.REQUEST need to be released explicitly with DBMS_LOCK.RELEASE. They are not implicitly released on COMMIT as other locks are. For example ...

        SQL> var handle varchar2(128);
        SQL> exec sys.dbms_lock.allocate_unique('MyLock', :handle);

        PL/SQL procedure successfully completed.

        SQL> select sys.dbms_lock.request(:handle) from dual;

        SYS.DBMS_LOCK.REQUEST(:HANDLE)
        ------------------------------
                                     0

        SQL> select count(*) from v$resource where type = 'UL';

          COUNT(*)
        ----------
                 1

        SQL> commit;

        Commit complete.

        SQL> select count(*) from v$resource where type = 'UL';

          COUNT(*)
        ----------
                 1

        SQL> select sys.dbms_lock.release(:handle) from dual;

        SYS.DBMS_LOCK.RELEASE(:HANDLE)
        ------------------------------
                                     0

        SQL> select count(*) from v$resource where type = 'UL';

          COUNT(*)
        ----------
                 0

        SQL>

Whenever I create a new version of an existing object this version is locked so that no one can modify the same object. This is done using the DBMS_LOCK package. Whenever I create a lock an enqueue resource entry is made. If I do not accept this object the lock (and its enqueue resource) is not released. I have certain transactions which have a large number of such unaccepted objects. This causes the error: ORA-00052: "maximum number of enqueue resources exceeded".