Problems with VB and ADO

i had some problems with the example about VB and ADO i found on
odbc.postresql.org :

i have a line like this :

rs.Open "SELECT id, data FROM vbtest", cn, adOpenDynamic

ok, my table is different, but the problem is that the recordset i obtain is
read only
unless i use the "adLockOptimistic" clause (which is not present in the
example)

another problem ( still not solved):

if i use rs.RecordCount i always obtain "-1" even if i use rs.MoveLast and
rs.MoveFirst.

My machine is a Win98
my server is Mandrake 8.1

thanx a lot

bye