Ive been getting this problem since the DLC update was released.
Specifically, it will begin the loading process, and just as it transitions into the loadout selection screen, it starts to freeze up and run very choppy. Mouse movement is unresponsive. And once it finally starts running smoothly again, it pops up with "retrying connection to server" and ultimately fails to connect.
The issue Im getting is exactly the one shown in this video https://www.youtube.com/watch?v=JMRyVcvIzqM
Im running dual AMD 7970 cards in crossfire mode. This issue only happens with crossfire enabled. It runs fine on a single card.
Heres my dxdiag
http://pastebin.com/U1XpGgJh