Hi Ashish
try these:
1) First of all, in your fork, right branch, where you are waiting for POSTED event, also receive the _EVT_CREATOR from the event (in the binding from event to WF) , if it is WF-BATCH, loop back to wait for event so that when posting is done from the Workflow, it does not ends itself. The completion of workflow will be taken care of by the other (parallel) branch of the fork
2) Yes, its confusing that why it is getting CANCELED. Is the MAIN workflow getting canceled? I doubt....it must only be the last few steps in the left hand branch (decision branch) of the fork; before those could be executed, the left branch of Wait event was over and thus nullified thosestep(s). Please confirm if the step status is CANCELED or the Main WF Status is canceled. If it's just the step, then point one would take care of it
3) If the MAIN WF gets canceled - then do check the workflow header-> the HAT icon-> Version Dependant Tab->Events Tab-> Check if POSTED is set to "CANCEL" the workflow (under Receiver type)....this could be causing the cancellation
Regards,
Modak