I've managed to solve this problem by adding a .htaccess file to the root of my webspace with the following contents (only the xap line is really necessary):
AddType application/x-silverlight-app .xap
AddType application/xaml+xml .xaml
AddType application/x-ms-xbap .xbap
might be worth a try for anyone else who runs into this problem and is hosting on Linux
I had to clear my browser cache before it would load again.