Virtual Boxがアンインストロールできない

Virtual Box をアンインストロールしたいのですがうまくいきません。

下記はターミナル上でアンインストロールの手順を踏んでいる時のコードです。
Welcome to the VirtualBox uninstaller script.

Warning! Found the following active VirtualBox processes:
2748 501 VBoxXPCOMIPCD
2750 501 VBoxSVC
2779 501 VBoxHeadless

We recommend that you quit all VirtualBox processes before
uninstalling the product.

Do you wish to continue none the less (Yes/No)?
Yes

The following files and directories (bundles) will be removed:
/Users/nathaniel/Library/LaunchAgents/org.virtualbox.vboxwebsrv.plist
/usr/local/bin/VirtualBox
/usr/local/bin/VBoxManage
/usr/local/bin/VBoxVRDP
/usr/local/bin/VBoxHeadless
/usr/local/bin/vboxwebsrv
/usr/local/bin/VBoxBugReport
/usr/local/bin/VBoxBalloonCtrl
/usr/local/bin/VBoxAutostart
/usr/local/bin/VBoxDTrace
/usr/local/bin/vbox-img
/Library/LaunchDaemons/org.virtualbox.startup.plist
/Library/Python/2.6/site-packages/vboxapi/VirtualBox_constants.py
/Library/Python/2.6/site-packages/vboxapi/VirtualBox_constants.pyc
/Library/Python/2.6/site-packages/vboxapi/init.py
/Library/Python/2.6/site-packages/vboxapi/init.pyc
/Library/Python/2.6/site-packages/vboxapi-1.0-py2.6.egg-info
/Library/Python/2.7/site-packages/vboxapi/VirtualBox_constants.py
/Library/Python/2.7/site-packages/vboxapi/VirtualBox_constants.pyc
/Library/Python/2.7/site-packages/vboxapi/init.py
/Library/Python/2.7/site-packages/vboxapi/init.pyc
/Library/Python/2.7/site-packages/vboxapi-1.0-py2.7.egg-info
/Library/Application Support/VirtualBox/LaunchDaemons/
/Library/Application Support/VirtualBox/VBoxDrv.kext/
/Library/Application Support/VirtualBox/VBoxUSB.kext/
/Library/Application Support/VirtualBox/VBoxNetFlt.kext/
/Library/Application Support/VirtualBox/VBoxNetAdp.kext/
/Applications/VirtualBox.app/
/Library/Python/2.6/site-packages/vboxapi/
/Library/Python/2.7/site-packages/vboxapi/

And the following KEXTs will be unloaded:
org.virtualbox.kext.VBoxUSB
org.virtualbox.kext.VBoxNetFlt
org.virtualbox.kext.VBoxNetAdp
org.virtualbox.kext.VBoxDrv

And the traces of following packages will be removed:
org.virtualbox.pkg.vboxkexts
org.virtualbox.pkg.virtualbox
org.virtualbox.pkg.virtualboxcli

Do you wish to uninstall VirtualBox (Yes/No)?
Yes

The uninstallation processes requires administrative privileges
because some of the installed files cannot be removed by a normal
user. You may be prompted for your password now...

Please enter nathaniel's password:
unloading org.virtualbox.kext.VBoxUSB
unloading org.virtualbox.kext.VBoxNetFlt
unloading org.virtualbox.kext.VBoxNetAdp
unloading org.virtualbox.kext.VBoxDrv
(kernel) Can't remove kext org.virtualbox.kext.VBoxDrv; services failed to terminate - 0xe00002c7.
Failed to unload org.virtualbox.kext.VBoxDrv - (iokit/common) unsupported function.
An error occurred durning 'sudo /sbin/kextunload -m org.virtualbox.kext.VBoxDrv', there should be a message above. (rc=3)
Failed to unload one or more KEXTs, please reboot the machine to complete the uninstall.
logout
Saving session...
...copying shared history...
...saving history...truncating history files...
...completed.