Firefox just released an update, 3.6.4, which runs plugins such as Silverlight and Flash in a separate process. Unfortunately, this breaks the ability of Visual Studio to debug Silverlight applications.
You can restore debugging functionality by not running plugins in a separate process. Do this by:
- In Firefox, in the navigation toolbar address field, go to about:config
- Accept the "This might void your warranty!" warning
- Find the preference option named: dom.ipc.plugins.enabled.npctrl.dll
- Double-click it to set its value to false
- Shut down all instances of Firefox and Visual Studio