That message is basically a result of a bug in error-handling logic; basically, an error is occurring while displaying the error. This can happen due to certain IIS or server settings, and in later version, you should see a more appropriate message. It's hard to say what the problem is, but if you didn't change anything, I would just reboot, and the problem might go away. Changing App Pool settings can also help (like Classic -> Integrated or viceversa). You can also try upgrading to see the underlying message. v4.6 is pretty old anyways.