Intermittend call transaction abends

[Becker Stephan (extern)]

Hi Workflowers,
 
since moving systems (system copy), we have problems with an old workflow
that still relies heavily on call transactions. About 20% of a given method
call abend with the following messages:
 
A E SY 002  / Protocol error when communicating with SAPGUI..
A E 00 359 /N         The transaction was terminated by the user
 
When I test the method through SWO1, it NEVER abends.
 
Has anyone seen something like this before? I have checked the
authorisations and setup of the WF-BATCH user, and there are no entries in
SM59.
 
We're on 4.6C.
 
Thanks,
Stephan