After several attempts of installing Silverlight in Firefox, it just doesn't work. Today I found out that one of my add-on, "No script" is causing Silverlight not to function correctly. A solution to this however is to right-click the NoScript icon and go to options, then uncheck the "forbid Silverlight" checkbox. Duh! While doing some further research, there are also other Firefox add-ons that can cause such issues, but most likely it has to be something related to media and such. Hope this helps some people.