This is a very reproducible bug. Make a new silverlight project. On the page.xaml, add a button. In that button's click event, set the button itself to invisible. Clicking the button will throw an exception (the button's click event passes, but the exception is caught in the Application_UnhandledException method in App.xaml):

Message "Error HRESULT E_FAIL has been returned from a call to a COM component."

at MS.Internal.XcpImports.MethodEx(IntPtr ptr, String name, CValue[] cvData)
at System.Windows.DependencyObject.MethodEx(String methodName, CValue[] cvData)
at System.Windows.UIElement.ReleaseMouseCapture()
at System.Windows.Controls.Primitives.ButtonBase.ReleaseMouseCaptureInternal()
at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(Object sender, MouseButtonEventArgs e)
at System.Windows.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, String eventName)

This seems too obvious a bug, so maybe there's something messed up with my install or machine - but everything else in Silverlight is working great.

Here's my exact code:

Page.xaml:

<UserControl x:Class="ErrorMouseButton.Page"
xmlns="http://schemas.microsoft.com/client/2007"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Width="400" Height="300">

<Canvas>
  <StackPanel>
    <TextBlock x:Name="Txt1" Text="Hello World"></TextBlock>
    <Button x:Name="Btn1" Content="Click Me" Click="Button_Click" />
  </StackPanel>
</Canvas>
</UserControl>
 

Page.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace ErrorMouseButton
{
  public partial class Page : UserControl
{
public Page()
{
  InitializeComponent();
}

private void Button_Click(object sender, RoutedEventArgs e)
{
  this.Txt1.Text += ".";
  this.Btn1.Visibility = Visibility.Collapsed;
}
}
}