Today we had a few people having problems with mumble dropping connection right after a connection was established.
To get around this problem try the following.
Click on the "configure" tab on your mumble window then click on "settings"
After entering settings click on the "advanced" box on lower left
After entering advanced settings click on "network" and then uncheck the "use Quality of Service" box, press "apply" and then "ok". You should now be able to connect to mumble.
Thanks to Armageddon for bringing this to our attention.