Problem In VB6 Application With SQL Server 2005

I have got a VB6 application where I update local SQL server table from MS Access table with code like that:

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Dim rst As ADODB.Recordset
Set rst = New ADODB.Recordset
rst.Open "SELECT * FROM Table1 WHERE [Fld1]=" & v1, Cn, adOpenKeyset, adLockOptimistic
'check if exist if not exist create new
If rst.EOF Then
rst.AddNew
rst("Fld1") = v1
rst("Fld2") = v2
rst.Update
End If

rst.Close
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On rst.Update I have got an error message that the server has to be added to syservers as linked with stored procedure sp_addlinked srever. Why?

Anyhow I executed the stored procedure then I've got error message 16933, "The cursor does not include the table being modified or the table is not updatable through the cursor."

I had to rewrite the code to "INSERT INTO (Fld1, Fld2..." and it works.

Is something wrong in SQL Server 2005 installation or any other reason?

Please help.