Commented Issue: FileNotFoundException occurred [19680]

I get this message when I use IntegerUpDown in my wpf application.

Could not load file or assembly 'Xceed.Wpf.Toolkit.Aero2, Version=1.9.0.0, Culture=neutral, PublicKeyToken=3e4669d2f30244f4' or one of its dependencies. The system cannot find the file specified.

The problem only occurs on my windows 8 computer and not on my windows 7.
Comments: ** Comment from web user: serj1980 **

System try to load different assemblies depend on Windows Theme. If I change theme to classic I have "Could not load file or assembly 'Xceed.Wpf.Toolkit.classic, .." error.