Stuttering graphics in my case is caused by having a directx overlay enabled with PlayClaw (like FRAPS)... if I close playclaw then the gameplay is smooth.... maybe the same with other overlays... can somebody with FRAPS test this and report back please? Also, with PlayClaw open, changing most settings in the VideoRes screen and hitting 'Apply' causes the game to close, again, closing PlayClaw resolves this issue. I can also play with FXAA on, on all 3 screens after closing PlayClaw. HDR on still causes only the 2 outside monitors to go black though, but this seems to be a known issue. I though I'd put this here as a solved to help others in the same situation, I hope it is not out of context!
Do not use PlayClaw. I also had problems with PlayClaw running. Now I'm using FRAPS, and so far I have no serious problem.