Have you tried the kernel from 'current' rather than 1.4.2, I had to do this
on my IIvx.
----------
>From: Brett Kessler <kesslerb@algorithmics.com>
>To: "NetBSD Mailing List (E-mail)" <port-mac68k@netbsd.org>
>Subject: RE: YA "Cannot mount root" error
>Date: Sat, Jun 24, 2000, 6:46 am
>

>Brendan,
>
>> Oh, you don't need to install it, just select the Boot Options menu in the
>> booter and then select MacOS file and when it brings up the file selection
>> dialog select the netbsd.GENERICSBC.gz, thenclick ok save the options and
>> boot...
>
>Thanks for the tip; I just tried it, and things are actually worse.  I
>copied the file to the internal 80MB hard drive (the only place with a Mac
>OS file system), changed the kernel location in the Booter application, and
>started the boot process.
>
>What followed was a constant stream of parity errors.  Rebooting with the
>generic (non-SBC) kernel got rid of the parity problem, so I know it's not a
>true SCSI problem.  Grrr.
>
>Anybody have any other ideas?