Report set stops working

We are having this strange issue with one of our scheduled report set consisting of the following programs:

1. Invoice Validation (20)

2. Invoice Approval Workflow (30)  

3. Payables Accounting Process (40)

4. Payables Transfer to General Ledger (50)

Whenever we re-start the server the report set runs on the scheduled time, however the 'To Date' in the parameter of accounting process defaults to some earler date and hence no data gets accounted and transfer. We then have to recreate the schedule the set.

Any idea as why this is happening and how to fix?

Thanks

Naushad