asp.net works fine in debug mode and gives oracle error when published to iis 7

I have an asp.net 3.5 website that connects to oracle database. when I work inside visual studio 2008 and test website for a heavy resource consuming page it works fine. but when I publish this site to IIS 7 (on windows server 2008, or windows 7) it causes oracl开发者_StackOverflow社区e listener to fall down. any ideas on what might cause this problem is welcomed.

ErrorMessage: ORA-12516: TNS:listener could not find available handler with matching protocol. Stack

StackTrace: at System.Data.OracleClient.OracleException.Check(OciErrorHandle errorHandle, Int32 rc) at System.Data.OracleClient.OracleInternalConnection.OpenOnLocalTransaction(String userName, String password, String serverName, Boolean integratedSecurity, Boolean unicode, Boolean omitOracleConnectionName) at System.Data.OracleClient.OracleInternalConnection..ctor(OracleConnectionString connectionOptions) at System.Data.OracleClient.OracleConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject) at System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup) at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) at System.Data.OracleClient.OracleConnection.Open() at DMS.Data.Database.DatabaseConnection.getCommand(String sqlString, Boolean isTransaction) in E:\DMS WORK\CRM9\db\DatabaseConnection.cs:line 561 at DMS.Data.Database.DatabaseConnection.CreateDatasetWithoutTransaction(String sqlString) in E:\DMS WORK\CRM9\db\DatabaseConnection.cs:line 878 at DMS.CRM.Today.FillRep() in e:\DMS WORK\CRM9\DMSCRM\today.aspx.cs:line 160 at DMS.CRM.Today.Page_Load(Object sender, EventArgs e) in e:\DMS WORK\CRM9\DMSCRM\today.aspx.cs:line 65 at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) at System.Web.UI.Control.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

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Is this 32-bit or 64-bit windows? If it is 64-bit then you need to install oracle 64-bit drivers along with the 32-bit drivers. or change your application build to x86 only.