As i mentioned in my original post rebuild ends without error and the webservice works as expected. Today we made a test running Visual Studio with Administrator Rights. In this case loading the source file with IntelliSense update ends within a few seconds. But there is still the loading error.
There are actually 2 open incidents (with RPI) for each of the problems (2804043 and 2804209).
Freundliche Grüsse
Werner Lanter