Diagnosis
There was a graphical event in the multiplexer callback process. Thecallback process cannot deal with the event because no multiplexerinstance exists.

Procedure
Correct the call method.
The reference variable GMUX in the interface file must be filled ONCEby the application (CREATE MIX).
If you want to process the event yourself in PAI, then you must notregister the MUX callback for this event (see graphics proxy's methodGP_REGEVENT).
Also make sure that the method CL_GFW_MUX=>ACTIVATEis called in PBO.