- Restarting your browser (closing it completely and restarting it)
- Clearing your cookies
- Clearing the Silverlight cache (right click on the Silverlight loading screen to bring up Silverlight preferences, delete application storage)
- Uninstalling and reinstalling Silverlight
And yes, Silverlight has plenty of problems. DASH streaming (which unlocks HTML5 players) only quite recently matured to a reliable, widely supported standard in terms of encrypted content. We'll migrate off Silverlight as soon as possible, but it's a pretty massive undertaking.