libvirt users - Jul 2012 - Attaching usb devices

Is the only way to attach a usb device to a vm first specifying the device,

     <hostdev mode='subsystem' type='usb'
managed='no'>
       <source>
         <vendor id='0x3080'/>
         <product id='0x1234'/>
       </source>
     </hostdev>

and then booting the vm while the device is attached? Can't I 
attach/detach a USB device to the vm later?  I did try the method 
suggested in 
http://david.wragg.org/blog/2009/03/usb-pass-through-with-libvirt-and-kvm.html 
but did not have much luck.

Also, can anyone explain me what happened in this log excerpt:

husb: open device 1.18
husb: grabbed usb device 1.18
husb: config #1 need 1
husb: 1 interfaces claimed for configuration 1
husb: device 1.18 disconnected

On Wed, Jul 18, 2012 at 01:30:18AM -0400, Mauricio Tavares
wrote:
> 	Is the only way to attach a usb device to a vm first specifying the
device,
> 
>     <hostdev mode='subsystem' type='usb'
managed='no'>
>       <source>
>         <vendor id='0x3080'/>
>         <product id='0x1234'/>
>       </source>
>     </hostdev>
> 
> and then booting the vm while the device is attached? Can't I
> attach/detach a USB device to the vm later?  I did try the method
> suggested in
http://david.wragg.org/blog/2009/03/usb-pass-through-with-libvirt-and-kvm.html
> but did not have much luck.
It is even worse than that if you have the same problem I
have: do your boot up with the device, then do some normal
things like disconnect the device, close up your laptop and
go to the coffee shop, do some work on the host machine, then
return home and try to get it to work again... you might
have the VM totally lock up... but in any case you may well
have to use FORCE to kill it so you can restart with the
USB device re-attached.

In my case it is a Mustek A3USB 1200 Pro which has to run off
a 32b VM since the linux drivers do not work with 64b code; I
run it in an Ubuntu jaunty release as that is the newest one
in which I can get their package to work.