Are you on El Capitan on your Mac by chance? I'm on a Mac as well. From my readings on several forums it sounds like Virtual box is a no go or at least unreliable fit on El Capitan at the moment. If you need it now, I've read that those using Parallels, VMware, or Boot Camping have had good results. I'm going to set up a Boot Camp partition to get around it myself. That way I don't have to wait for any other vendor other than Apple to upgrade their drivers.