Workflow definition of task 'WS900123456' cannot be activated

Hello Experts,

I am trying to activate a workflow on document event change, and i am getting this error in the event trace: Workflow definition of task 'WS90123456' cannot be activated

In the receiver data i have:

receiver type : ws90123456

object key:

receiver fm: SWW_WI_CREATE_VIA_EVENT_IBF

rfc destination:

check fm

receiver type fm:

message: Workflow definition of task 'WS90123456' cannot be activated

any ideas as to why this is happening ?

points are awarded,

regards