I never had any troubles with my XmlFormView control until only recently.
To not open forms from the "Form Templates" library (admin deployed forms with managed code) I switched to another library and set "Allow
management of content types" to "Yes". Next I added my published form from the existing content types list to that library.
Opening the form in my browser works like a charm. Copying the url and setting it as XmlFormView.XsnLocation doesn't work at all. Any suggestions?