A Geforce 660 Ti is most certainly *NOT* a GTX 680, high end nVIDIA GPU. It is a mid-High, and thus, a couple of large notches below the high end for its generation. I can imagine that choosing too high of a game setting can do what happened to you, and probably other anomalous behaviors.
i know what my card is, and what it isnt. It is a card which can run BF3 on Ultra (!) with 45 fps constantly. It runs AC4 on highest settings (except AA) and Crysis 3 on high. This game has a 10 year old engine, even on the highest settings it should run in like 200 fps. I would say its just awefully optimized, but googling the issue, many people have the same problem with much better hardware.
edit: And it doesnt explain why the connection to the server is lost. That has nothing to do with the graphics card.
