Are you using Anonymizer?
If the answer is yes - that's why.
If no - then close your game.
Visit https://modxvm.com/
Login with your account.
Activate XVM.
And now start the game.
I was having the same issue -- turned out to be an old mod that I had created that included SWF's that have worked for multiple patches -- but finally got in the way. this may not apply to you -- but oddly I was seeing the same behavior.
Make sure you do not have any old "favorite" mods in use.