error during executing a job

hi...
can anybody help me out in this error ?I'm getting this following error when trying to execute a job.

SQL>execute dbms_job.run(54);
BEGIN dbms_job.run(54); END;

*
ERROR at line 1:
ORA-12011: execution of 1 jobs failed
ORA-06512: at "SYS.DBMS_IJOB", line 406
ORA-06512: at "SYS.DBMS_JOB", line 272
ORA-06512: at line 1


This job refreshes a materialized view .. i've checked the status of the materialized view and its dependencies.. everything is in valid state ....

even i tried to refresh those mviews.. that also fails with these errors

SQL>execute dbms_refresh.refresh('SP_CM_MV_SHIPTO_CONTRACTS');
BEGIN dbms_refresh.refresh('SP_CM_MV_SHIPTO_CONTRACTS'); END;

*
ERROR at line 1:
ORA-04045: errors during recompilation/revalidation of SPORTAL.SP_CM_MV_SHIPTO_CONTRACTS
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 794
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 851
ORA-06512: at "SYS.DBMS_IREFRESH", line 683
ORA-06512: at "SYS.DBMS_REFRESH", line 195
ORA-06512: at line 1


SQL>execute dbms_refresh.refresh('SP_CUSTOMERMASTER_MV_SHIPTO');
BEGIN dbms_refresh.refresh('SP_CUSTOMERMASTER_MV_SHIPTO'); END;

*
ERROR at line 1:
ORA-04045: errors during recompilation/revalidation of SPORTAL.SP_CUSTOMERMASTER_MV_SHIPTO
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 794
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 851
ORA-06512: at "SYS.DBMS_IREFRESH", line 683
ORA-06512: at "SYS.DBMS_REFRESH", line 195
ORA-06512: at line 1

Can anybody help?