The only time I have run into something like this is for usb devices that the
host cannot handle. For example, I have a music player that Linux does not
recognize. It won't work in a Windows VM running on Linux because the host
cannot detect it and pass it along. This would not appear to be the case in your
situation since the devices show and you say they are detected. As was said
previously some versions of VirtualBox do not support usb shared devices, but
your version shows them so it must support usb device sharing.

I saw your thread on VirtualBox forums. There are a couple of good points made
here. One is mounting. If it is mounted in the host then it will be unavailable
in the guest (except for CD and DVD drives where you have pass through enabled).
Secondly you can control which ones are available to the guest once they are
unmounted in the host from the menu bar of VirtualBox. By checking the boxes
here they are enabled for use in the guest OS.
If you cant get it going you have other options such as VMWare server.