Hi Jurgen, thanks for responding. I had already looked at the long text for BA235 in the job log. It tells me that there has been an error, but unfortunately it doesn't tell me any details of the error, or how to find them. There are no earlier errors in the job log. So it isn't possible to follow the advice to contact SAP with precise details.
It reads:
Diagnosis
An function module from the Archive Development Kit (ADK) was called after an error had occurred in a previous call. Consequently, the processing by ADK was terminated.
Procedure
If the current program is an SAP program, contact SAP with precise details of the error. If the current program is a customer program, you should adjust the program to avoid this error.