Kellu,
I'm certainly not an expert in VM, having only ever had a virtual XP Pro on a Vista workstation. In that situation, as it happens I was using Inventor 2011 and Adobe CS3. but the performance in 3D applications was terrible- it took forever to load and then was extremely sluggish. It was so poor that I didn't look too far into the problem- I bought Windows 7 and ran everything in native 64-bit Win 7 Ultimate. The only thought I had at the time was that there was some kind of conflict between drivers when running some kind of emulation mode, that is XP driver on the VM had to be translated into Vsta drivers..
The other possibility is that Inventor has been redesigned since the 2011 version and the older version was not...