popup window is minimizing when it opens

I have a pop window to display a note but it appears and then minimizes as the page behind seems to be doing a postback.  I have traced the code and the postback occurs before the popup window code runs but visibly the window appears to redraw after the popup appears.  Here's my code under button to call poopup.

Protected Sub wgNote_ClickCellButton(ByVal sender As Object, ByVal e As Infragistics.WebUI.UltraWebGrid.CellEventArgs) Handles wgNote.ClickCellButton
        Dim Value As String
        Dim FacilityId As String

        Value = e.Cell.Row.Cells(1).Value
        facilityid = e.Cell.Row.Cells(2).Value

        System.Web.HttpContext.Current.Response.Write("<SCRIPT LANGUAGE=""JavaScript"">" & vbCrLf)
        System.Web.HttpContext.Current.Response.Write("my_window=window.open('" & "NotePopupFacility.aspx?NoteID=" & Value & "&Facilityid=" & FacilityId & "', '','width=600,height=450,resizable=no,status=no,menubar=no,scrollbars=yes,toolbar=no');")
        System.Web.HttpContext.Current.Response.Write("</SCRIPT>")
    End Sub