Ubuntu – How to force the installation of the Virtualbox Extension pack

I have a BIG problem with VirtualBox; every time I try to add or install the newest extension pack, it gives an error; at first, it asked me to add my user to the vboxuser group, which I already did, but still can't install the extensions pack.

How can I force Virtualbox to install it?

It says, Failed to install extension pack—the path to the file, and the error itself.

Here I tried running it on the root terminal, but Virtualbox crashes.

 uri-MS-7267 uri # virtualbox
 Qt CRITICAL: Qt-subapplication(20282)/kdeui (KIconLoader): Error: standard icon theme "oxygen" not found! 

 Qt WARNING: QPainter::begin: Paint device returned engine == 0, type: 3
 Qt WARNING: QPainter::setCompositionMode: Painter not active
 Qt WARNING: QPainter::end: Painter not active, aborted
 Qt WARNING: QPainter::begin: Paint device returned engine == 0, type: 3
 Qt WARNING: QPainter::setCompositionMode: Painter not active
 Qt WARNING: QPainter::end: Painter not active, aborted
 Segementation fault

When trying to install the Extpack from the terminal i get this:

 uri@uri-MS-7267 ~ $ sudo VBoxManage extpack install Oracle_VM_VirtualBox_Extension_Pack-4.0.10- 72436.vbox-extpack
 0%...
 Progress state: NS_ERROR_FAILURE
 VBoxManage: error: Failed to install "/home/uri/Oracle_VM_VirtualBox_Extension_Pack-  4.0.10-72436.vbox-extpack": The installer failed with exit code 1: VBoxExtPackHelperApp:   error: The owner is not root: '/usr/lib'

And I get nothing when using gksu.

 uri@uri-MS-7267 ~ $ gksu VBoxManage extpack install Oracle_VM_VirtualBox_Extension_Pack-4.0.10-72436.vbox-extpack
 uri@uri-MS-7267 ~ $