Workflow triggering twice

Hi,

I am have created a workflow for PO change I am using buisness object BUS2012 and event changed .

as start event everything work fine but workflow is triggering twice when PO is changed.

I observed the event trace and found chaging the PO trigger two changed event but secand one is for different BO ie, FREBUS2012.

How to solve this ?

Regards

Bikas