We have had one client install the module, and place it on a page. Nothing was showing when the page was viewed. No ability to see the module at all.
This turned out to be a problem with the IIS settings not being configured for xaml. On all our test systems, and a windows 2003 out of the box install, IIS is correctly configured.
If you have a system with this problem, the solution is to enable xaml mime type support in IIS. Attached is a VB script to enable this.
NOTE: All care and no responsibility for this script.
Thanks to Jens Lewald for the script.