I have Ubuntu 14.04 LTS and just installed the latest Virtualbox 4.3 to use Windows 7. As explained here : Set up Usb-stick for Virtualbox ; I added myself to the vboxusers and also installed the extension pack.
However I still cannot make VirtualBox to detect any of my sticks, in order to add it to the filter list in the VM settings. There is still no Virtualbox version for 14.04, may this be an issue?