I attached a screenshot to show what I mean.  Basically when I try to show any html page in the xamwebhtmlviewer, even though the control is inside a canvas on a child window, the actual html shows up outside the window.  When I move the mouse to the top of the child window, the html suddenly snaps back inside the child window.  Here is the xaml.  In the codebehind all I do is set the SourceURI property.

<controls:ChildWindow x:Class="Comdata.PdfViewer"
           xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
           xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
           xmlns:controls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls"
           Width="824" Height="824"
           Title="PdfViewer"  xmlns:ig="http://infragistics.com/Controls">
    <Canvas Name="panMain">
        <Button x:Name="OKButton" Content="OK" Width="75" Height="23" HorizontalAlignment="Right" Canvas.Left="731" Canvas.Top="0" />
        <ig:XamWebHtmlViewer Canvas.Left="0" Canvas.Top="29" Name="htmlView" Width="806" Height="760" />
    </Canvas>
</controls:ChildWindow>