Have a problem to update the fields to trigger integration event through web service

Hi There,

I have a problem to update the fields to trigger integration event through web service.

I have set up the work flow to track the changing of some opportunities' fields.  

And there are two actions of my work flow.  First action is to trigger an integration event.  The second one is to send out an email notification.  I aslo did a test through the onDemand web page.  Both actions would be done after I changed the related the fields.  That means my work flow is working.

But if I update those fields through the web service.  I will get the email only.  It seems the integration event is not triggered. That is really weird to me.