GWT and Loadrunner: issues with GWT DFE

Hello,

I would like to test a GWT web application using loadrunner but I'm having issues using the GWT DFE chain

I followed what is described in this tutorial video http://www.youtube.com/watch?v=ASD8xj0otUk

but in my case the strings serialized by GWT are not turned into an XML format (so i cannot make any correlation on the data) 

I cannot see any error in the code generation panel so I'm assuming that the GWT DFE is applyied correctly (and the WAR that I used is correct)

Do you have any suggestion on what I can check in order to find the problem?

I'm using loadrunner 11.51

thanks