In our asp.net 2.0 application we have the an HttpModule and HttpHandler. They are registered in web.config to handle requests for certain file types. 
The request is initiated asynchronously from client side using MS AJAX.
I noticed something strange:
HttpHandler:ProcessRequest is not entered on every HttpModule:EndRequest which seems like incorrect behavior since my understanding of the flow of events:
HttpModule:BeginRequest > HttpHandler:ProcessRequest > HttpModule:EndRequest. For some reason, the handler part is sometimes skipped.
What could be causing this?