Problem with 6.4 and "createdb -D"

i've just gotten around to upgrading to 6.4 on a couple of FreeBSD (2.2.7)
servers, and i'm having problems creating databases in alternate locations.
basically, here's what i did:

1) dumped the data from a 6.3.2 install
2) compiled 6.4 (completely generically -- configure; make; make install)
3) did the initdb, then started the postmaster
4) did an "initlocation /mnt/ccd2/pgdata"
5) tried to "createdb -D /mnt/ccd2/pgdata test", which gave me the following
error:
www:/~:[11:42am]45% createdb -D /mnt/ccd2/pgdata test
ERROR:  Unable to locate path '/mnt/ccd2/pgdata/test'
        This may be due to a missing environment variable in the server
createdb: database creation failed on test.

the same createdb command works fine on my 6.3.2 install.

what is the error referring to? has anyone else seen this problem?