VMware for Developers
With the recent release of Mountain Lion DP2 some problems cropped up with Fusion 4.1 (you’ll need a developer account to view that link.) Luckily the new VMware Fusion Technology Preview 2012 makes it possible to run the latest Mountain Lion release without any problems. This preview release also allows you to keep Fusion 4.1 installed if you encounter any problems in other virtual machines: the only requirement is that you can only run one version at a time.
After several freezes, the technology preview worked for me. It seems strange that the VMs would be so hard to get working when not even using the VMware Tools.