Gopi,
From the support side, we have 3 SAP KBAs about this type of error. See if any of it helps you out.
- http://service.sap.com/sap/support/notes/2097205
- http://service.sap.com/sap/support/notes/1997005
- http://service.sap.com/sap/support/notes/2139535
Both of them tied to configuration in the configPanel.
Documentation about SAP Work Manager located under:
http://service.sap.com/instguides -> Select SAP Mobile -> SAP Work Manager 6.2. Double check the configuration documentation link and find how to change the assignment type and they have example in the back.
Check if yours is related to the documents above or check the main documentation.
Best Regards,
Mark Pe
SAP Platinum Support Engineer