If you get VERR_NEM_MISSING_KERNEL_API VirtualBox and attempting to fall back to NEM, then follow the suggestions mentioned here.

Fix VERR_SUP_VP_THREAD_NOT_ALONE, VirtualBox Error in supR3HardenedWinReSpawn, by following the solutions mentioned in this article.

Version 3.1 of Sun's VirtualBox hosted virtualization software gains new features such as Teleportation, snapshots, and 2D acceleration ...