[omniORB] user exception thrown client gets CORBA::SystemException

[Lolke B. Dijkstra]

Hi,
 From the server I throw a dicom::ObjectNotFound exception.
The server says:

omniORB: WARNING -- method 'getName' on: root<0>
 raised the exception: IDL:dijkstra-ict.com/dicom/ObjectNotFound:1.0

The client says:
omniORB: LocateRequest to remote: root<0>
omniORB: throw UNKNOWN from GIOP_C.cc:247 (MAYBE,UNKNOWN_UserException)
Caught CORBA::SystemException.2:1330446337

Where the last string is the result of:
    catch(CORBA::SystemException& e) {
        cerr << "Caught CORBA::SystemException." << e.completed() << ':' 
<< e.minor() << endl;
    }

I try to catch the dicom.ObjectNotFound exception but the catch clause 
does not seem to work. Instead the SystemException is caught.
Anybody knows why this is?

Kind regards,
Lolke