If a job has scedule defined and its created in SQL Server 2005, when you script it out using SSMs 2008, the job script will have Invalid parameter @schedule_uid is added for the call of sp_add_jobschedule. Due to this the script fails when run against 2005 server.
The same issue occurs when you try to migrate jobs from 2008 server to 2005 server using 'Transfer Jobs Task' of SSIS 2008. The task fails with error
[Transfer Jobs Task] Error: Execution failed with the following error: "@schedule_uid is not a parameter for procedure sp_add_jobschedule.
Warning: Non-existent step referenced by @on_success_step_id.
Warning: Non-existent step referenced by @on_fail_step_id.
Warning: Non-existent step referenced by @on_fail_step_id.".