treeview disappeared when i reopen the form - vb.net

Question

I would like to ask for your help. I am stuck to this for more than two days, I've searched the net but unfortunately got no answer.
I have a program in vb 2008 and a database (SQL Server 2008). I have this form which contains treeview. The items display is selected from the database. When i run the program and open the form the treeview items displayed (at first), but when i closed the form and try to open it again the treeview disappear. I dont know why :( . Why is it disappearing? Can somebody help me please. Thank you.
Below is my code....
#form_load
Private Sub frmProfile_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Call conecDB()
Call initCMD()
FillTable()
CreateTree() 'create the treeview node
findNode() 'find and checked the selected nodes that was given to the profile
End Sub
'the functions
Private Sub FillTable()
'tv1.Nodes.Clear()
dtable.Columns.Add("ID", GetType(Integer))
dtable.Columns.Add("NAME", GetType(String))
dtable.Columns.Add("PARENT", GetType(Integer))
dtable.Columns.Add("LEVEL", GetType(Integer))
qSQL = "select mod_id,name,parent,level,sort,mnu_name from module where status='A' and parent!=-1"
With comDB
.CommandText = qSQL
rdDB = .ExecuteReader
End With
Do While rdDB.Read
dtable.Rows.Add(rdDB!mod_id, rdDB!name.ToString(), rdDB!parent)
My.Application.DoEvents()
Loop
For i = 0 To dtable.Rows.Count - 1
Dim ID1 As String = dtable.Rows(i).Item("ID").ToString
dtable.Rows(i).Item("LEVEL") = FindLevel(ID1, 0)
Next
rdDB.Close()
End Sub
Private Function FindLevel(ByVal ID As String, ByRef Level As Integer) As Integer
For i = 0 To dtable.Rows.Count - 1
Dim ID1 As String = dtable.Rows(i).Item("ID").ToString
Dim Parent1 As String = dtable.Rows(i).Item("PARENT").ToString
If ID = ID1 Then
If Parent1 = 0 Then
Return Level
Else
Level += 1
FindLevel(Parent1, Level)
End If
End If
Next
Return Level
End Function
Private Sub CreateTree()
tv1.Nodes.Clear()
Dim MaxLevel1 As Integer = CInt(dtable.Compute("MAX(LEVEL)", ""))
Dim i, j As Integer
For i = 0 To MaxLevel1
Dim Rows1() As DataRow = dtable.Select("LEVEL = " & i)
For j = 0 To Rows1.Count - 1
Dim ID1 As String = Rows1(j).Item("ID").ToString
Dim Name1 As String = Rows1(j).Item("NAME").ToString
'Dim mName As String = Rows1(j).Item("mNAME").ToString
Dim Parent1 As String = Rows1(j).Item("PARENT").ToString
If Parent1 = 0 Then
tv1.Nodes.Add(ID1, Name1)
Else
Dim TreeNodes1() As TreeNode = tv1.Nodes.Find(Parent1, True)
If TreeNodes1.Length > 0 Then
TreeNodes1(0).Nodes.Add(ID1, Name1)
End If
End If
Next
Next
End Sub
Private Sub findNode()
Dim rName As String = String.Empty
Dim b As Boolean = True
qSQL = "select access_id,mnu_name from profile_details where prof_id=" & lblPID.Text & ""
With comDB
.CommandText = qSQL
rdDB = .ExecuteReader
End With
Do While rdDB.Read
rName = rdDB!access_id.ToString()
Try
Dim arr As TreeNode() = tv1.Nodes.Find(rName, b)
For i = 0 To arr.Length - 1
tv1.SelectedNode = arr(i)
tv1.SelectedNode.Checked = True
Next
Catch
MsgBox(Err)
End Try
Loop
rdDB.Close()
End Sub