I have recently installed virtualbox on my ubuntu and I could not get usb devices to work.
This is because in order for virtualbox to use your usb resources it is required that the current user is added to the virtual box user group
sudo usermod -a -G vboxusers bizmate
Where vboxusers is the group and bizmate is the username
After you have run the above you will need to log out and in again before the changes are committed.
I hope this helps