Hi Andy,
Your panic log shows that your machine does not have an inconsistent installation in the same way as that of killerdemouches, but it also does not implicate VMware Fusion at all, and strongly suggests either a hardware problem with your MacBookPro6,2 or a problem with the Nvidia display driver in Mac OS 10.8.4. In fact, your panic log looks very similar to that in the thread "My MacBook Pro keeps crashing" in the Apple Support Communities. You may wish to follow the advice posted by Linc Davis in that thread.
I'm not aware of any safe way to back out a Mac OS update.
Cheers,
--
Darius