You probably made a similar mistake as I did, and mistakenly filed a PR on 
it. If it was to be wd* at umass, it would have to be an ATAPI device. 
This is not.

IIRC, you need
scsibus* at scsi?
umass* at usb?
sd* at scsibus?

I have the same device and it works fine as long as you don't accidently 
comment out scsibus* at scsi? as of 1.6Q

-- 

The nice thing about Windows is - It does not just crash, it displays a
dialog box and lets you press 'OK' first.
						-- Arno Schaefer