I guess I met the same prolem.  I ran, sudo nvram boot-args=debug=0x10 in terminal and but it didn't fix all the problem. By the way, I do see Enable VT-x/AMD-V and Enable Nested Paging are both checked in the Acceleration tab under System in the Virtual Box settings.  Do anybody have any suggestion what I should try next? Thanks.  ... View more

Have you tried the solutions posted above? Enabling Intel-VT /AMD-V in the BIOS? Checking for conflicting virtualization platforms, checking the hash of the downloaded image, etc? ... View more