dbms_job failures

I have a procedure that should be run daily. This is how I submitted the job:

dbms_job.submit( :jobid,

'FIT_DBA.AMS_JOB.PURGE_AMS_TAB;',

                              trunc( sysdate ),


                              'round( trunc( sysdate ) + 1.20, 'HH' )');

I've had it in the queue a number of days and noticed that Failures = 13. When I try to run it using,

    dbms_job.run(61)
I get an error ORA-12011 'execution of one jobs failed.' I also have errors in sys.dbms_ijob line 405 and sys.dbms_job line 267.

The next_date is calculated and displayed correctly which according to O'Reilly, 'Oracle Build Packages' should not happen if the job fails.

If I run this code
  begin

        FIT_DBA.AMS_JOB.PURGE_AMS_TAB;
  end;
the procedure runs without error.

The job is submitted and run under user 'FIT' which has rights to run any procedure.

Why would the job fail?

Thanks.

--
Jim Poe (jpoe_at_fulcrumit.com)