ODBC longvarchar error - why does this not work?

I am trying to use Visio enterprise in conjunction with PostgreSQL 7.0.2 via
the ODBC driver (6.5). It works perfectly except for one small issue -
longvarchar types do not work. I have searched the archives and tried a
number of different ODBC driver settings (unknown as LONGVARCHAR, TEXT as
LONGVACHAR, PARSE STATEMENTS, etc) with no success. The relevant portion of
the ODBC log is included below. As you can see, I have two fields defined as
LONGVARCHAR. Tables without longvarchar fields are created without any
errors.

conn=131151048, query='BEGIN'
conn=131151048, query='create table practice ( practice_id INTEGER not
null, practice_des LONGVARCHAR, practice_inst LONGVARCHAR, pop_up_def
VARCHAR(250), constraint practice_pk primary key (practice_id) ) '
ERROR from backend during send_query: 'ERROR: Unable to locate type name
'longvarchar' in catalog'

Thanks for your help.

- Adam