a previous thread has exposed the firewire code in NetBSD-Current is still
under development. It can't attach devices yet. People doing work on it know
this.

so, the question probably reduces back to the USB case. The diagnostics from
the USB options in the kernel can help a lot here, working out which frob is
needed. 

	is you USB 1.0 or 1.0+lies or 2.0 ? (typically 1.0+lies is called 2.0 :-)

	is the device attached, and turned on at boot time, or post boot?


the first one is about how successfully the two things, computer and disk USB 
can converge on the USB state. 

the second one is about how successfully NetBSD can converge on attaching
some memory to the USB->UMASS->SCSI->sd<x> sequence of 'things' in kernel.

This is also known about, the memory concerned fragments over time.
Somebody in core is aiming to re-work it to deal with fragmented memory
(either by re-coelescing it, or <handwaving> I don't understand here and
believe me, I don't understand a LOT :-)

I had these problems with an Archos USB2.0 MP3 unit which pre-dates the iPod btw.