I have been using Geoserver WFS and WMS with Qgis for a longtime. Now i am trying to integrate WPS... I downloaded and activated WPS plugin for Geoserver. And i succesfully got result of buffer example with WPS Request Builder of Geoserver. But when i try with QGIS WPS-Client i never got result. It sends the data to server but never comes back the result. it stucks... I tried official 52North WPS server and i got result succesfully. So what should i do ???
I'm not sure but best bet would be to look at the underlying response coming back (Just because it wasnt able to be shown does not mean there was no response) from the server I'm not familiar with QGIS but if you get web/network debugging tool like fiddler it can capture the request and let you look at what the server is actually sending back.
Second avenue of investigation is to take look at your webserver, and geoserver log files for information at the time of the request. If you post that back here others will be better able to help.