Steps to reproduce.

1. Drag a RadPropertyGrid to a form.
2. Set the selected object to a button for example.
3. Set the System.Threading.Thread.CurrentThread.CurrentUICulture to bg-BG for example
4. Run the project and try to edit the Size property. You will see that it is displayed in the format X;Y, but you have to enter string in the X,Y format otherwise you get an exception.