New Post: WPF-Application with delays after Update to Windows7

I've found know a non-Beta version 4.1.26, which I have installed with Nuget. The delay-problem doesn't disappear. I try to change the call of 50 RaisePropertyChanged to one call of RaisePropertyChanged(""). This works (Thank You!) but the delay is still the same. So I think it is not a problem of MVVM-Light.
Nevertheless, I would be glad, if anybody can help me with an idea about this issue.