As the title states, since updating, I can no longer test on any device. I've tried rolling back versions and can no longer find a proper combination that works, so this has become a really urgent issue for us. I have tried repairing, rebooting, restarting, and reinstalling several versions. Current versions listed below, everything is fully up to date.
Build Host - 126.96.36.199
Xamarin.iOS - 188.8.131.52
Xamarin - 184.108.40.206
Xamarin.iOS - 220.127.116.11
Running Visual Studio 2013 on Windows 8.1
Build Host lives in OS X 10.9.5