I’m not sure if this has been fixed in .NET 4, but WPF has never picked up the current culture when rendering things like currency or dates. It’s something I consider a massive oversight, but thankfully is easily corrected.
In your App class:
protected override void OnStartup(StartupEventArgs e)
{
FrameworkElement.LanguageProperty.OverrideMetadata(
typeof(FrameworkElement),
new FrameworkPropertyMetadata(
XmlLanguage.GetLanguage(
CultureInfo.CurrentCulture.IetfLanguageTag)));
base.OnStartup(e);
}
See this excellent post for more information.