Windows Form integrated with Sql Server Connection Error

HI guys i have created a windows form application in visual studio 2012. In the load of the form i load a couple of datatables. But everytime one of the clients machine tries to access the server it gives them this error: A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: SSL Provider, error: 0 - The wait operation timed out.) i did a little research and started writing in CMD "Netsh Winsock Reset" then the program will connect and work fine. But every time they restart the machine it will not connect to the sql server.

Here a example of my code:

Public lector As SqlDataReaderPublic adapter AsNew SqlDataAdapterPublic comando AsNew SqlCommandPublic con AsNew SqlConnection(Data Source=Sqlserver;Initial Catalog=ROPDB;Persist Security Info=True;User ID=UserID;Password=**********)
PrivateSub MainForm_Load(sender AsObject, e As EventArgs)HandlesMyBase.LoadTry
            dtpEffective.Value =Date.Today
            dtpExpiration.Value = dtpEffective.Value.AddYears(3)

            txtUsername.Text = My.Settings.Username

            lblstripFecha1.Text =Date.Today.ToLongDateString

            adapter =New SqlDataAdapter("Select * From Bank", con)
            Bancos.Clear()
            adapter.Fill(Bancos)
            adapter.Dispose()
            cmbBanks1.DataSource = Bancos
            cmbBanks1.DisplayMember ="Name"
            cmbBanks1.ValueMember ="CODE"
            cmbBanks1.Refresh()
            cmbBanks1.SelectedIndex =-1