This error seems to be popping up with Lion and Oracle VirtualBox Failed to load VMMR0.r0 (VERR_SUPLIB_WORLD_WRITABLE). Unknown error creating VM (VERR_SUPLIB_WORLD_WRITABLE) Some users get this error because /usr is world writable. I checked mine, it was ok. Also went through Disk Utility and repaired permissions. Also set the .vdi file to 755. No luck I then changed /Applications and /Applications/VirtualBox.app to 755, #sudo chmod 755 /Applications #sudo chmod 755 /Applications/Virtualbox.app Works now (I also upgraded to latest .app and extension file) I have no idea why these files are set world writable!