I remember seeing that error popping up before they patched an issue in 6.1
That particular issue somehow deleted the schedule on the client manager:
Build 6.1.0.377 of Master
CSCuj57105: Unable to insert job due to start date is not part of compiled schedule
Problem : When the master compiles a new day's schedule, it first deletes any existing Schedule record before creating a new one. The query used also gets executed on the client manager, but can get executed out of order there causing the newly created Schedule to be immediately deleted.
Solution : Use the ID not the production date to delete old Schedule records to prevent the client manager from immediately deleting newly created Schedule records during a compile.
Anyway, when we were experiencing this issue, I had to work around it by inserting the job using a job action and associated email event. Inserting any job manually didn't work.
