Worklist bulk/mass changes AR31 -> 'No Administrator for this tas k found'

[LANGE, BODO]

Hi Workflow community,
I have a pretty strange behaviour of my 4.6C SP 34 when it comes to bulk changes
of a Worklist using AR31. The system offers basically either a standard workflow or
the possibility to resolve everything within the code of the transaction.
I do not use the standard workflow WS00000025 but have customized the substitutes so
that the system should somehow pull one of the standard tasks 00007956,
57, 58 depending on what type of change/worklist is done. So when I launch AR31 with my worklist
the only thing I get is a popup saying 'No administrator found' and my worklist in display
mode. I have checked enqueue and dequeue logs, and the SWW_CONT it seems as if all parameters
are passed to the task, besides the WF_INITIATOR. Unfortunately I did not find a system
which does not use the standard workflow 25 so far and where the alternative, the usage of the
application and auto-forwarding, works properly. Has anybody out there encountered this
behaviour and maybe resolved this issue?
 
Since I am not very familiar with the application side, maybe someone can shed some light on this.
 
 
Thanx a million,
Bodo