Either there's a bug in the grid, or there's a new way to apply image to a button and I'm not aware of it.

Dim but As New myButtonCol
        With but
            .ImageList = imgMore
            .ButtonImageIndex = 0
            .AllowSorting = False
            .Width = 16
            .AllowSizing = False
        End With
        dgQueries.Columns.Items.Add(but)
        dgQueries.Columns.Items(2).ShowTooltips = False
        ConnectToButtonColumn(dgQueries, 2)

Private Sub ConnectToButtonColumn(ByVal flygrid As FlyGrid, ByVal indexOfButtonColumn As Integer)
        Dim bc As myButtonCol = DirectCast(FlyGrid.Columns.Items(indexOfButtonColumn), myButtonCol)
       MoreOption(dgFields, m_dsFields.Tables(0))
End Sub

[c#]
private void MakeBitmapTransparent(Bitmap bmp)
{
   bmp.MakeTransparent();
}