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 22.214.171.1247 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.
I saw this problem the very first time I was running 6.2 as well. The very next day, I had compiled schedules again - So the problem should go away the following day - Did you experience it resolving itself the next day as well?
Are you using an Oracle database? If so, you need to replace the ojdbc7.jar file with ojdbc6.jar file in the lib folder on your Client Manager. Cisco had us do this and it resolved the problem. I don't know the details, but Cisco said the ojdbd7.jar was more stringent. This also fixed a problem where only the first hundred Interactive Users were being displayed out of 1000+ records.