Strange bug with Silverlight.
I have created a slideshow using the css transform property and translateX to move between the content items. If Silverlight is initialised without windowless = true, it disappears.
To show Silverlight after applying a css transform I had to use:
<param name="windowless" value="true" />
Hope this helps if anyone encounters the same bug.
UPDATE: Got the same problem with disqus. Applied position relative to disqus container and the problem is “fixed”