Postgres datetime() error

[Justin Kamerman]

I have GnuCash up and running on RedHat 9.0 with the following packages
installed

gnucash-1.8.1-3
gnucash-backend-postgres-1.8.1-3

on my front end and Postgres 7.4.2 on the database server. I can save an
empty account register, ie no accounts, to the database. This creates a
new database and tables in Postgres as expected. When I add a new
account and try to save to the database GnuCash complains:

The server at URL postgres://<mydbserver>/<databasename> experienced an
error or encountered bad or corrupt data.

The Postgres log reflects:

ERROR:  function datetime("unknown") does not exist
HINT:  No function matches the given name and argument types. You may
need to add explicit type casts.
ERROR:  current transaction is aborted, commands ignored until end of
transaction block

Does anyone have any suggestions what my problem is or is this perhaps a
bug ?

Regards

Justin Kamerman