in main module, I created sub for testing like
   Public Sub test()
       Dim oConn As Oracle.DataAccess.Client.OracleConnection

       oConn = New Oracle.DataAccess.Client.OracleConnection("User
ID=user;Password=user;Data Source=XE;Statement Cache Size=16")
       oConn.Open()
   End Sub

and everything is ok.
previously, I had the same statement in one library (inside the solution),
and everything was also ok.
now, when I start an application (as an standalone, rebuilded), it's also
all ok.

what did I changed?

there is a main form that I show now, and I call another form for choosing
the database, and after that I create a selected db connection and load
data.

this is in main form:

   Private Sub frmMain_Shown(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Shown
       fSelectDB = New frmSelectDB
       fSelectDB.jClearList()
       For x As Int32 = 1 To oSettings.DB_Count
           fSelectDB.jAddItem(x, oSettings.Databases(x).DBName)
       Next
       'fSelectDB.MdiParent = Me
       fSelectDB.TopMost = True
       fSelectDB.ShowDialog()
       Timer1.Start()

   End Sub

this is in frmSelectDB:
   Private Sub cmdSelect_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles cmdSelect.Click
       If Me._lista.SelectedIndex > -1 Then
           oSettings.OpenDB =
Val(Mid$(Me._lista.Items(Me._lista.SelectedIndex).ToString, 1, 1))
           LoadDB()
       End If
   End Sub

and there is LoadDB to load the data.
program stopps in LoadDB, there is a call to a library where is opening
database (in opening connection everything stops).

How do I stop debuggin? I simply need to restart computer (sometimes with
reset), because cpu usage goes to a maximum.