I experience the same one...
The problem infact is that the Portable VirtualBox is not supplied with VirtualBox usb driver, so everyone who tries to connect anything to usb port won't see nothing but an error until the host OS will have THAT driver been installed.
So, dear creators of Portable-VirtualBox, all the progressive humanity asks you to extract the VirtualBox usb driver from original distributive of VirtualBox to a separate folder