For what it's worth, I have just verified this problem on my system.
I was trying to install on Postgres 6.5.3 (Stable Debian) to see
if ACS/pg might work under those conditions.  However, my 7.0 setup
which used to work, now doesn't.  (And yes, I did make the necessary
changes to load-data-models, postgres.sql, etc.)

I get the same error complaining about "No such function 'bpchar'
with the specified attributes

So, let's chalk it up to Postgres and move on.  That's what I'm going
to do, at any rate