Anyone else having this issue? After fixing the crashing issue by installing it directly onto the C drive, the first mission went completely fine, no issues. Then I start Mission 2 and all of a sudden it is lagging quite badly. Animations are slower, the mouse seems less responsive and it takes about 3 or 4 seconds for the shots to be shown hitting something. It even lags when hovering over the main menu selections. Anyone else having this problem/found a potential workaround? Running Windows 8.1 64 Bit.

I'm having the same issue.

The first session I played up to mission 3 was fine, but now whether I start a new campaign or load a save game I always get the lag or slowdown or whatever it is.