By default, 10.6 should be able to run 32 bit and 64 bit apps in the same environment, as the kernel can boot in 32 bit mode and run 64 bit apps if required.

I believe the only exception is when you force 10.6 to boot into 64 bit mode, then you'll have probs with 32 bit apps.

I'm sure Autodesk will come out with a service pack which will allow 10.6 installation.

-J