Nothing.
Just a black screen. Alt+Tabbing out did nothing. Hitting Esc did nothing. After about 10 - 15 minutes I simply ALT+F4'ed out.
This is new behavior, never experienced it until this patch.
EDIT: Reload, see my mech is still in game so I click a different one and press launch. Instantly I get "Cannot find match" dialog. Not a few seconds or minutes later, literally as I press the launch button.
/Not liking patch so far...
Edited by Serapth, 01 October 2013 - 01:26 PM.