Figured I’d pass this around if someone searches on it:
basically if you have elements on the page that use z-index, ie. I have a yahoo menu that has dropdown selections. By default the menu items are obscured by the silverlight control.
To fix this problem, you can set parameters on the silverlight object/control:
<param name="windowless" value="true" />
You can also set other properties like transparent background:
<param name="background" value="transparent" />
(Edited for comment below)