I believe this is a GE question, but who knows? It may be an artifact of the way OSM does things. By the way, I just found out about OSM this past weekend. Great work! I am a big fan of the Open* movement.
So, I included the OSM KMZ link as an overlay in google earth (http://www.markus-bader.de/osm/OpenStreetMapLayer.kmz) and that works, but the google satellite images show through. I see the transparency slider, and I have adjusted it all the way to the right, which should be fully opaque, but it is not. I have never tried adding any other external overlays, so I don’t know if this is always the case for all such overlays, but it is for this one. Did I do it wrong? I added the link by using the “Add” menu, and then “Network”.