According to Stephen Ma:
>
>Make sure your /etc/disktab is current - the vnode device now requires
>a valid disklabel to be installed (unless you're accessing vnd0d),
>with a correct partition type. Old /etc/disktab didn't include the
>partition type for floppy3 and floppy5.
>

Bingo - that was it.  Works fine with the new disktab :-)

-- 
Brett Lymn, Computer Systems Administrator, British Aerospace Australia
===============================================================================
  +++ Divide By Cucumber Error.  Please Reinstall Universe And Reboot +++
  - Hogfather, Terry Pratchett.