Job fail issue with Reporting Agent pre calculation

We have a prototype 3.5 system up and running and have been experimenting with pre-calculation of web templates using the Reporting Agent.

When Scheduling the package the job always fails with the following error:

"System error in program CL_RSR_REQUEST and form SAVE_TO_DATA_STORE:UNKNOWN_HANDLE"

Does anyone know what could be the source of this problem? Any help appreciated.

thanks

Mike