Sorry about not replying earlier on what I did to fix my pkgsrc and 
pkg_add problems, but I got so busy I didn't have time.

I updated to the latest version of /usr/src via CVS from the 1.6 
release branch.
Then I treated it like a security update (since I really don't quite 
know all that the following incantation does, in particular the 
usetools part):

  cd /usr/src/usr.sbin/pkg_install
  make USETOOLS=no cleandir dependall
  make USETOOLS=no install

Both pkg_add and building packages from source now work.

-- 
Tom Jernigan, Oak Ridge National Laboratory
Presently at General Atomics, San Diego, California (858) 455-4122