ORA-12571: TNS:packet writer in ASP.NET app

Hi,

All my ASP.NET applications sends me the error "ORA-12571: TNS Packet writer" once a day when they runs the first time. This error appears early in the morning when the web applications connects to Oracle and they try to execute any code in the database. If the web page runs again the error will not appear anymore.
The client (webserver) runs on Windows 2000 Server/Framework 1.1, ODP.NET 9.2.0.2.102. The database version is Oracle 9.2.0.1 and runs on Windows 2000 Server and AIX 5.1. The connection error appears on both databases.

These are some errors that sends me the app:


Oracle.DataAccess.Client.OracleException ORA-12571: TNS Packet writer failure at Oracle.DataAccess.Client.OracleException.HandleErrorHelper(Int32 errCode, OracleConnection conn, IntPtr opsErrCtx, IntPtr opsSqlCtx, Object src, String procedure, String[] args)
at Oracle.DataAccess.Client.OracleException.HandleError(Int32 errCode, OracleConnection conn, String procedure, IntPtr opsErrCtx, IntPtr opsSqlCtx, Object src, String[] args)
at Oracle.DataAccess.Client.OracleCommand.ExecuteReader(Boolean requery, Boolean fillRequest, CommandBehavior behavior)
at Oracle.DataAccess.Client.OracleDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable)
at cursos.Global.Session_Start(Object sender, EventArgs e)
at System.Web.SessionState.SessionStateModule.CompleteAcquireState()
at System.Web.SessionState.SessionStateModule.BeginAcquireState(Object source, EventArgs e, AsyncCallback cb, Object extraData)
at System.Web.AsyncEventExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

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Oracle.DataAccess.Client.OracleException ORA-12571: TNSacket writer failure at Oracle.DataAccess.Client.OracleException.HandleErrorHelper(Int32 errCode, OracleConnection conn, IntPtr opsErrCtx, IntPtr opsSqlCtx, Object src, String procedure, String[] args)
at Oracle.DataAccess.Client.OracleException.HandleError(Int32 errCode, OracleConnection conn, String procedure, IntPtr opsErrCtx, IntPtr opsSqlCtx, Object src, String[] args)
at Oracle.DataAccess.Client.OracleCommand.ExecuteNonQuery()
at replicacion.process_replic.Replica(String strActivo, Int32 iParte, Int32 iReplicaSisipa)


Any comment that helps to solve this problem will be very appreciated.

Thank you in advance for your help.

Regards