An error has occurred: Error connecting to the server: Kerberos 5 authentication not supported

I am trying to connect to my PostgreSQL server using kerberos. I
received the pgAdmin III message in the title line.
I am able to connect to the PostgreSQL server via ssl using md5 password
authentication using pgAdmin III.
Kerberos is working for file and mail services on the same server. Is
this a pgAdmin II problem or a problem with
PostgreSQL configuration files??

Thanks.

System details:

Server:   Mac OSX 10.4.8
PostgreSQL:   8.1.5
pgAdmin III:  1.6RC2

pg_hba authentication:  krb5
keytab location in pg_hba.conf:  /usr/local/pgsql/data/krb5.keytab
keytab location for other services: /etc/krb5.keytab

environment parameters set:  PGREALM, PGKRBSRVNAME

Randall Williams