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"Troubleshooting: SSIS Package Execution Using SQL Server Agent (SQL Server Video)" at http://msdn.microsoft.com/en-us/library/dd440760(SQL.100).aspx">http://msdn.microsoft.com/en-us/library/dd440760(SQL.100).aspx .

"An SSiS package does not run when you call the SSIS package from a SQL Server Agent job step" (support article), at http://support.microsoft.com/kb/918760