yes i am running vista 64 on this macpro.
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This should be ok.
What buffer size did you select in the driver dialog of your audio interface? MIR supports only powers of two (28,256, 512...), any other buffer size should cause a warning (we had crashes with older versions there).
Do you see an ASIO driver for your mbox 2 in the audio settings dialog of Vienna Ensemble?
What happens exactly, when you start the engine - do you see a blue status bar at the bottom (indicating the progress of impulse response preprocessing) or does it crash right after you press the button?
Oh, and did you already try Asio4All?
This might help to figure out if there's just a problem with your rig kontrol or a general issue with MIR on your machine.
I hope we can figure out what's wrong here, Florian