Tracked down to a bug in MSVCR120.DLL, the ball is in Microsoft's camp. On the user side, the workaround is to update to Win7 SP1. On our side, the workaround is to detect FMA3 and if not present, disable it manually via _set_FMA3_enable(0) because Microsoft's are too incompetent to do it themselves.
I'm not going to work on that, fwiw.
I'm not going to work on that, fwiw.