Can't unload kext while installing VirtualBox 4.3.6

Question

Downloaded VirtualBox 4.3.6 and after attempting to install in Mavericks (OSX 10.9.1) I get a generic error "The installation failed".

Going through the logs and after running the uninstall tool I arrived at the conclusion that VirtualBox cannot unload there particular kernel extensions: org.virtualbox.kext.VBoxUSB, and org.virtualbox.kext.VBoxDrv.

The exact errors are:

(kernel) Can't unload kext org.virtualbox.kext.VBoxUSB; classes have instances:
(kernel)     Kext org.virtualbox.kext.VBoxUSB class org_virtualbox_VBoxUSB has 1 instance.
Failed to unload org.virtualbox.kext.VBoxUSB - (libkern/kext) kext is in use or retained (cannot unload).
(kernel) Can't remove kext org.virtualbox.kext.VBoxDrv; services failed to terminate - 0xdc008018.
Failed to unload org.virtualbox.kext.VBoxDrv - (libkern/kext) kext is in use or retained (cannot unload).

Manually attempting to unload the kexts with sudo kextunload -b org.virtualbox.kext.VBoxUSB produces exact results.

Is there any way to remove these? I ran the VirtualBox uninstaller so I'm positive I don't need these for anything else yet they are preventing me from doing a clean VirtualBox install.

Answer 1

Repaired disk permissions, rebooted, ran uninstall script again, and the next installation was successful.

Answer 2

I was able to clean install 4.3.22-98236-OSX (which I had originally), but upgrading to 4.3.30-101610-OSX OR 5.0.0-101573-OSX would fail and throw an error during installation.

Removing /mach_kernel folder solved the "Failed to install" issue for me.