Serial columns and ADO

As far as I understand, since the driver exposes 'serial' columns
as 'AutoNumber', ADO issues 'SELECT @@IDENTITY' to retreive the new
generated values just after inserts. The driver, in turn, has to modify that
query into 'SELECT currval(...)'.

When working with PG tables from inside MS Access, it all works perfectly!
But here is a small test suite that doesn't work as expected:

----------------------------------------------------------------------------
Server side:

CREATE TABLE t1
(
  col1 serial NOT NULL,
  col2 varchar(50)
)
WITHOUT OIDS;

Client side (Visual Basic 6.0 or VBA):

Sub Test()
  Dim strSql As String
  Dim cn As New ADODB.Connection
  Dim rs As New ADODB.Recordset

  cn.Open "Provider=MSDASQL.1;Data Source=Test_pg;"

  strSql = "SELECT * FROM t1"

  rs.ActiveConnection = cn
  rs.CursorLocation = adUseClient
  rs.CursorType = adOpenStatic
  rs.LockType = adLockOptimistic
  rs.Source = strSql

  rs.Open

  rs.AddNew
  rs("col2") = "Sample string"
  rs.Update
  MsgBox rs("col1")

  rs.Close
End Sub
----------------------------------------------------------------------------

Try this and you will see '0' in the messagebox shown and the entries in
psqlodbc_xxxx.log similar to the following:

.................
conn=04973D90, query='INSERT INTO "public"."t1" ("col2") VALUES (E'Sample
string')'
conn=04973D90, query='SELECT 0'
.................

My environment:
PostgreSQL 8.1.0 backend
ODBC driver 08.02.0200 Unicode (the latest at the moment of writing) on
WinXP SP2

Any ideas?
Dmitry.