OLEDB update/insert from data array failing data adapter update

[mwenz]

I am trying to update an Access table using OLEDB in VB.Net 2005. I can add rows but I cannot update them.

Code to instantiate the Access database and table...

        Dim conn As New OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & db.Name)
conn.Open()
Dim oda As New OleDb.OleDbDataAdapter("select " & sqlCols & " from [" & txtOutputTable.Text.Trim & "];", conn)
Dim cb As New OleDb.OleDbCommandBuilder(oda)
cb.QuotePrefix = "["
cb.QuoteSuffix = "]"
oda.UpdateCommand = cb.GetUpdateCommand
oda.InsertCommand = cb.GetInsertCommand
oda.DeleteCommand = cb.GetDeleteCommand
Dim ds As New DataSet
oda.Fill(ds, txtOutputTable.Text.Trim)

<sqlCols> contains the column names I want to update/insert delimited by [ and ]. This may or may not include all columns in the table but that's the point. I want to facilitate doing whatever a user asks for, potentially augmenting existing data with new colums for the same key. This is why I only specify the columns I need to work with in data adapter. The key is date and hour of the day (1 - 24). By the time the code gets here that table structure contains all needed columns.

The program then goes off to another source and builds a data array based upon time range and data items. Date and hour are the first two columns and the remaining data fleshes out the rest of the columns. This data may need to update the table contents or be inserted. The data array def is as follows:

Dim da(iHrs, iCols) As Object

Code to build dataset for update from the data array:

For i = 0 To da.GetUpperBound(0)
    ds.Tables(0).BeginLoadData()
    Dim dr(da.GetUpperBound(1) + 1) As Object
    dr(0) = CDate(da(i, 0).ToString.Substring(0, 11))
    dr(1) = da(i, 0).ToString.Substring(12, 2)
    For j = 1 To da.GetUpperBound(1)
        dr(j + 1) = da(i, j)
    Next
    ds.Tables(0).LoadDataRow(dr, False)
    ds.Tables(0).EndLoadData()
Next

Code to update the data adapter...

Try
    oda.Update(ds, txtOutputTable.Text.Trim)
Catch ex As Exception
    MsgBox(ex.Message)
End Try

The oda.Update fails saying it's trying to create duplicate values in the index, primary key, or relationship. The primary key is the first two columns of each dr. There are no relationships so I have to assume the update is defaulting to insert all the time instead of choosing update where required. I've been working under the premise that if I define the appropriate data adapter commands, OLEDB figures out what needs to be updated or inserted and "magic happens" (I know, very naive of me). Obviously this is not the case but I do not know how to fix it short of going back to dao and doing FindFirst's or Seek's and proceeding accordingly.