When you create a maintenance plan job by login your own user name and password, you are locked with that. SQL server agent job will create with that ownership.
----------------------2008--------------------------
Verify if there are any users created any SSIS other than “sa”
select a.name as JobName, b.name as OwnerName from
msdb..sysssispackages a
inner join Master.dbo.syslogins b
on a.ownersid = b.sid
/* Fix */
UPDATE msdb..sysssispackages
SET ownersid = 0x01 ---- sa account
WHERE name = 'test'
