SQL & PL/SQL

I want to refresh a materialized view, but I get an ORA-12008 error.
Does anybody have an idea? I do not find any errors in my refresh statement.

CREATE MATERIALIZED VIEW scott.dummy_mv
  TABLESPACE test
  BUILD IMMEDIATE
  USING INDEX TABLESPACE idx_test
  REFRESH 
     START WITH sysdate 
     NEXT ROUND(SYSDATE)+5/24		
     WITH PRIMARY KEY
  ENABLE QUERY REWRITE
  AS
  SELECT KM.ID ID
          ,KM.USERNAME USERNAME
	  ,KM.ABTID ABTID	
  FROM my_table KM
/

scott@orcl>desc dummy_mv
 Name                                      Null?    Typ
 ----------------------------------------- -------- ----------------------------
 ID                                        NOT NULL NUMBER(4)
 USERNAME                                  NOT NULL VARCHAR2(30)
 ABTID                                     NOT NULL NUMBER(4)

scott@orcl>


BEGIN 
  SYS.DBMS_JOB.REMOVE(6579);
COMMIT;
END;
/

DECLARE
  X NUMBER;
BEGIN
  SYS.DBMS_JOB.SUBMIT
  ( job       => X 
   ,what      => 'dbms_refresh.refresh(''"scott"."dummy_mv"'');'
   ,next_date => to_date('07.01.2009 05:00:00','dd/mm/yyyy hh24:mi:ss')
   ,interval  => 'ROUND(SYSDATE)+5/24              '
   ,no_parse  => FALSE
  );
  SYS.DBMS_OUTPUT.PUT_LINE('Job Number is: ' || to_char(x));
COMMIT;
END;
/

scott@orcl>exec dbms_refresh.refresh('dummy_mv');
BEGIN dbms_refresh.refresh('dummy_mv'); END;

*
FEHLER in Zeile 1:
ORA-12008: error in materialized view refresh path
ORA-00947: not enough values
ORA-06512: in "SYS.DBMS_SNAPSHOT", Zeile 820
ORA-06512: in "SYS.DBMS_SNAPSHOT", Zeile 877
ORA-06512: in "SYS.DBMS_IREFRESH", Zeile 683
ORA-06512: in "SYS.DBMS_REFRESH", Zeile 195
ORA-06512: in Zeile 1

scott@orcl>