I'm trying to install a QGIS web server on windows 7 (64 bit), and request maps on HTTP. I followed this tutorial: http://hub.qgis.org/projects/quantum-gis/wiki/QGIS_Server_Tutorial
I installed apache separately (via xampp), because if I installed it via the osgeo4w setup, it gave me errors saying that the DLLs of IPP codec pack are missing. I also disabled FastCGI, because that gave me some other kind of errors. Now I got to the point where the server works, it starts up, and it answers to requests on HTTP. The problem is that it always sends back a black white picture. I checked the .qgis project file several times and everything is fine. I tryed adding layers through WMS to the QGIS desktop app, and I was successfull, and got a nice map in the desktop app.
What could the problem be, why does the server send back a blank picture?