Black screen sounds like a rendering issue. If you try Firefox in Safe Mode it will disable hardware acceleration temporarily. If its Silverlight specific [https://msdn.microsoft.com/en-us/library/ee309563%28v=vs.95%29.aspx more reference to how it works in the extension] but it notes that acceleration is turned on for Intel processors after 2004. If that does not work I might suggest to reinstall Silverlight.