Silverlight custom control inheritance issue

So, I have the following control in SL4...

XAML:

<Canvas x:Class="LineAnnotation"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Canvas.Left="0" Canvas.Top="0" Loaded="Canvas_Loaded"  >
</Canvas>

CodeBehind:

public partial class LineAnnotation : Canvas
    {


        public LineAnnotation()
        {
            InitializeComponent();

        }


        void Canvas_Loaded(object sender, RoutedEventArgs e)
        {
            this.Height = ((Canvas)this.Parent).Height;
            this.Width = ((Canvas)this.Parent).Width;
        }
    }

This class works fine, I can instantiate and use it. However, I have another control that subclasses this one:

public class ArrowAnnotation : LineAnnotation
{

    public ArrowAnnotation() : base() 
    {
        // Some other init stuff
    }

} 

When i try to instantiate one of these in my code, I get the following exception:

System.Windows.Markup.XamlParseException: Failed to assign to property 'System.Windows.FrameworkElement.Loaded'. [Line: 5 Position: 47]
   at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
   at LineAnnotation.InitializeComponent()
   at LineAnnotation..ctor()

It's not just the Loaded event, it can be any event handler, I get the same exception. This code happens to be shared with a WPF project and this works fine. any idea what the problem is here?

EDIT: I realized that ArrowAnnotation need not be a partial class as there is no xaml. changing this made no difference.