The Visual Studio 2008 Designer doesn't seem to like UserControls that reference the MVVM-Light ViewModelLocator. I get an error message like:

Could not create an instance of type 'MyUserControl'.

For example, the following XAML will cause this behavior if MyUserControl uses the ViewModelLocator to establish its DataContext.

<Page x:Class="MyProject.Views.MainView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Views="clr-namespace:MyProject.Views"
>
    <Grid>
        <Views:MyUserControl/>
    </Grid>
</Page>

Is the ViewModelLocator only meant to be used in top-level Views?