Ran into the same issue after installing, tried going back to a earlier version of Silverlight but to no avail.
But now there is a update to Maxwell Render, appears they have moved away from Silverlight & now supports Sketchup 2013.

Here is the link to the Maxwell's website
http://www.maxwellrender.com/forum/viewtopic.php?f=107&t=40712&sid=5e2cd8d5040be25d6c31bb6f68b92c4d 😄