Not sure if this is related to dual-CPU GPUs or something else, but I only got a black screen after completing the mission (with both alternatives ending). The dialog and music keep rolling but the screen just fades to black. After waiting for a moment I noticed pressing spacebar helps to get to the final mission as it skips the credits.

I don't have any deep knowledge about dual-CPU GPU problem, but the thought just crossed my mind that since some of the PiP-screens in game flash black (because the game-engine doesn't know how to properly communicate with both cores?), maybe the end credits get assigned to wrong core making the screen just stay black. Again, I hardly have a clue what I'm talking about but maybe that might help.

My setup:
i7 3770K 3,4GHz
GTX 690
16 GB 2133MHz RAM.