Vista - Displaying an icon in a menu item

Should be simple as pie. Using Expression Blend 2 September Preview the icon
will display properly in the MenuItem in the design mode but when I run the
application the icon disappears. What am I missing?

Thanks.

Here's the code:

<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="Window1"
x:Name="wndMain"
Title="Window1"
Width="640" Height="480">

<Grid x:Name="gridRoot">
<Menu HorizontalAlignment="Stretch" VerticalAlignment="Top"
x:Name="menuMain">
<MenuItem x:Name="mnuiFile" Header="_File">
<MenuItem x:Name="mnuiFile_Close" Header="_Close">
<MenuItem.Icon>
<Image Source="graphics/error.ico" Height="15" Width="15"
Stretch="Fill"/>
</MenuItem.Icon>
</MenuItem>
</MenuItem>
</Menu>
</Grid>
</Window>