DataGridView - Loading Each Table Of XML File?

I am facing a "weird" problem with the DataGridView. In fact, I have a function, that loads each table of an xml file into a datagridview (27 tables all with same structure except one called Listes). In the datagridview I have a combobox column to select "type" (it's the 3rd Column, so it's index is 2 normally). The problem is that when I call the function loaddata for the first time, all work perfectly ! If I call it for a second time, to reload the data, I get an error of cast! I verified and it seems that first time I call the function the column that contains the combobox is column(2), but when I run it again automatically the indexes of the columns are changing and am getting the error, because the column that contains the combobox is becoming column (3) and that explains the cast error because the column'(2) is not anymore the combobox so the cast will fail ! What I can't understand is why it's reordering that way my columns automatically ?

Here is the code:
vb.net
Sub LoadData(Path As String )
Dim oData As DataSet
oData = New DataSet
oData.ReadXml(Path)
Dim i As Integer
Dim MaGrille As DataGridView
[Code] .....