I don't remember where I got pkgsrc from, but I would guess that it
  was whatever pkgsrc-current was on July, 20th, 2005.

It might have been broken.  I'd try updating, and removing all your
mk.conf hacks and trying again.

  To summarize: is it correct to say that I should download the head of the
  pkgsrc-2005Q2 branch (any pointers from which directory to download it?
  I haven't looked yet, but I don't remember seeing directories with 2005Q2
  in their names) to go together with the netbsd-2-0/200508040000Z that I
  already have?

It's a branch tag.   'cvs up -r pkgsrc-2005Q2' in pkgsrc.  But head
should be fine too.

-- 
        Greg Troxel <gdt@ir.bbn.com>