dbms_refresh.add seems to hang

I have an Oracle 11 database and was given a script that creates a refresh group, a MV and then tries to add the materialized view to the refresh group using dbms_refresh.add and that statement hangs. The creation of the group and MV return no errors. the script is run as 'SYS'. Any help is greatly appreciated -

— create group

execute

DBMS_REFRESH.MAKE(name => 'XOWN.MV_WEEKLY', list => '', next_date=>SYSDATE, interval=>'null');

— create mv

CREATE MATERIALIZED VIEW XOWN.PS_TBL
(ERNCD,EFFDT,EFF_STATUS,DESCR)
TABLESPACE USERS
NOCACHE
NOLOGGING
NOCOMPRESS
BUILD IMMEDIATE
USING INDEX
TABLESPACE USERS