Beepin' and Boopin' thats what robots do

If you've tried to start up mumble today, you may have seen this error message: “A referral was returned by the server.”

the fix for that is here: http://blog.mumble.info/important-update-to-mumble-1-2-3a/

uninstall your current version and install the one from the top link on that page. certificates shouldn't be affected by this, and you should be able to log in immediately.

alternatively, download the fixed mumble.exe from the third link on that page, and replace that file in the directory in which mumble was originally installed on your computer.