Massive FPS Drop on High Spec Rig ?

[mZLY]

I'm getting a solid 60 FPS with no drops with SSAO samples set to 128 until a part of the game with speech, where it all goes to hell and I drop down to 15 FPS. My hardware and/or game settings aren't the problem. The 6970 is a fair bit more powerful than the 570 I believe.