Can't enter username in form with Silverlight
Lets assume you use Firefox browser (and have the plug in installed).

If the cookie information is displayed at the bottom of the login page, click on the Close button to hide the cookie information and then click back into the Username box. You should now be able to enter/type your usename.

If the cookie information is not displayed at the bottom of the login page, click on Tools and then Add-ons. This will open a new tab where you can view the Plugins you have installed. Once the new tab has appeared you can close it and then click back into the Username box. You should now be able to enter/type your usename.