I am trying to do a simple update to a dataset, and I get an error on da.update.

Public Sub UpdateCLastTestDate(ByVal strConnect As String)

Dim da As New OleDbDataAdapter()
Dim cn As New OleDbConnection(strConnect)
Dim cmd As New OleDbCommand("SELECT * FROM mcTestingReport", cn)
Dim ds As New DataSet()
Dim cb As OleDbCommandBuilder = New OleDbCommandBuilder(da)
da.SelectCommand = cmd
da.Fill(ds, "mcTestingReport")

Dim i As Integer



For i = 0 To ds.Tables("mcTestingReport").Rows.Count - 1

If Not IsDBNull(ds.Tables("mcTestingReport").Rows(i).Item("cLastTestDate")) Then
If ds.Tables("mcTestingReport").Rows(i).Item("cLastTestDate") > ds.Tables("mcTestingReport").Rows(i).Item("NextTestDate") Then
ds.Tables("mcTestingReport").Rows(i).Item("NextTestDate") = #1/1/1900#

End If
End If

Next i
da.Update(ds, "mcTestingReport")


cn.Close()

End Sub