I just tested it again and I don't get a crash with the scenario I described, but the control doesn't fill up it's parent grid like I expect. Here's the source:
Title="Window1" Height="300" Width="400">
<ve:VEMap HorizontalAlignment="Stretch" Width="400"/>
You can see the white background of the window on the sides of the map when you'd expect the map to fill the entire window. I also noticed that if I set the height to 300 then the map does fill the entire window.