Installation CD disabled during boot

["Niall O'Reilly" <Niall.oReilly+netbsd%no8.be@localhost>]

Hi.

I'm trying to install 6.1.4 from CD loaded in an external drive
connected to a USB3 port.  Boot menu appears as expected with 4
options (just install, install with ACPI disabled, install with
both ACPI and SMP disabled, exit to boot loader CLI).  Whichever
of the first 3 options I pick, just after wd0 is found, the
message 

  uhub0: device problem, disabling port 1

appears. Since this is where the optical drive is connected,
installation can't proceed.

This problem seems to me as if it may be related to that 
described at http://gnats.netbsd.org/46696

I've tried disabling USB3 support in the BIOS, but to no avail.
Is there something I may g=have overlooked, or should I report
a bug?

Best regards,
Niall O'Reilly