Fonte
http://www.webupd8.org/2011/04/virtualbox-ubuntu-1104-natty-narwhal.html
The VirtualBox repository (contrib) for Ubuntu 11.04 Natty Narwhal has finally been created today.
Besides the new Ubuntu 11.04 Natty Narwhal repository, there's also a new version: VirtualBox 4.0.6 which adds support for X.Org Server 1.10 final (for Guest Additions), some Linux Kernel 2.6.39-rc1 fixes as well as a fix for slow Linux guests with recent Kernels.
See the complete VirtualBox 4.0.6 changelog.
Install VirtualBox 4 in Ubuntu
Add the VirtualBox repository and install the latest VirtualBox 4.0.6 in Ubuntu 11.04 Natty Narwhal, 10.10 Maverick Meerkat or 10.04 Lucid Lynx using the commands below (before this, make sure you remove any VirtualBox 3.x version you may have installed):
echo "deb
http://download.virtualbox.org/virtualbox/debian $(lsb_release -sc) contrib" | sudo tee /etc/apt/sources.list.d/virtualbox.list
wget -q
http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc -O- | sudo apt-key add -
sudo apt-get update
sudo apt-get install virtualbox-4.0
For some additional features like USB 2.0 support, you'll have to install the VirtualBox Extension Pack which you can download from HERE. Once downloaded, double click the Extension Pack and it should open with VirtualBox and you can then easily install it. If that doesn't work for you, Open VirtualBox and go to File > Preferences and on the Extensions tab, click the "add" button on the right (first blue diamond) and browse for the VirtualBox extension pack.
And a note for those who use an older Ubuntu version and want to try out the latest Ubuntu 11.04 Natty Narwhal in VirtualBox: to install the Guest Additions in Ubuntu Natty (guest), all you have to do is run the following command:
O mais importante na instalação do virtualbox que estava faltando.
sudo apt-get install virtualbox-ose-guest-utils
Depois deste procedimento, com a inicialização do virtualbox as portas usb reconhecidas em 100%
