No matter where I am, Requiem always crashes every 15 or so minutes. I don't understand why, since I ran Overture and Black Plague perfectly fine.
Could it be some overheating on cpu / graphics card? Could you check the temperatures of those and make sure the fans are working properly?
If it is not hardware problem it is very hard to say what it might be. Is it any map especially that it crashes on? Or does it seem to be more time based?