The problem was caused because loObject was used in the uniqueness of the first method. When I changed it to this, it worked:

    ' Add a distributor
    ' expN1 Distributor primary key
    ' expN2 Handling fee
    Private Function AddDistributor(ByVal tnNoDistributor As Integer, ByVal tnHandlingFee As Double) As Boolean
        Dim lnNoDistributor As Integer = 0
        Dim loObject(2) As Object
        Dim loObject2(2) As Object

        ' See if it already exists
        For Each loObject2 In oDistributor
            lnNoDistributor = loObject2(1)

            ' If this is the one
            If lnNoDistributor = tnNoDistributor Then
                Return True
            End If

        Next

        loObject(1) = tnNoDistributor
        loObject(2) = tnHandlingFee

        oDistributor.Add(loObject)
        Return True
    End Function