nhibernate sql Express connection issue - error: 26 - Error Locating Server/Instance Specified

I can connect fine with normal ado.net. However i get the following error when i tried to connect nHibernate.

hibernate.cfg.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
  <session-factory>
    <property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property>
    <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>
    <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
    <property name="connection.connection_string">Server=xxxxx\SQLEXPRESS; Database=xxxxx; User ID=xxxxx; Password=xxxxx; Trusted_Connection=True</property>    
    <property name="proxyfactory.factory_class">NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property>
    <property name="show_sql">true</property>    
  </session-factory>
</hibernate-configuration>

Server error

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Full stack

[SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4845255 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194 System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +4858557 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +90 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +342 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +221 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +189 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +185 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +31 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +433 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +66 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +499 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 NHibernate.Connection.DriverConnectionProvider.GetConnection() +102 NHibernate.Tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.Prepare() +15 NHibernate.Tool.hbm2ddl.SchemaMetadataUpdater.GetReservedWords(Dialect dialect, IConnectionHelper connectionHelper) +65 NHibernate.Tool.hbm2ddl.SchemaMetadataUpdater.Update(ISessionFactory sessionFactory) +80 NHibernate.Impl.SessionFa开发者_运维问答ctoryImpl..ctor(Configuration cfg, IMapping mapping, Settings settings, EventListeners listeners) +599 NHibernate.Cfg.Configuration.BuildSessionFactory() +87 XXX.Domain.Repositories.NHibernateHelper.get_SessionFactory() in D:\dev\MyProject\XXX\XXX.Domain\Repositories\NHibernateHelper.cs:23 XXX.Domain.Repositories.NHibernateHelper.OpenSession() in D:\dev\MyProject\XXX\XXX.Domain\Repositories\NHibernateHelper.cs:31 XXX.Domain.Repositories.EntryRepository.GetCountByGmapId(Int32 gmapId) in D:\dev\MyProject\XXX\XXX.Domain\Repositories\EntryRepository.cs:152 XXX.Controls.Activity.BindRepeater(Int32 id) in D:\dev\MyProject\XXX\XXX.Controls\Activity.ascx.cs:58 XXX.Controls.Activity.DropDownListMaps_SelectedIndexChanged(Object sender, EventArgs e) in D:\dev\MyProject\XXX\XXX.Controls\Activity.ascx.cs:75 System.Web.UI.WebControls.ListControl.OnSelectedIndexChanged(EventArgs e) +111 System.Web.UI.WebControls.DropDownList.RaisePostDataChangedEvent() +134 System.Web.UI.WebControls.DropDownList.System.Web.UI.IPostBackDataHandler.RaisePostDataChangedEvent() +10 System.Web.UI.Page.RaiseChangedEvents() +165 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1485

From http://www.connectionstrings.com/ :

Server=myServerAddress;Database=myDataBase;
User ID=myUsername;Password=myPassword;Trusted_Connection=False;

I would try setting Trusted_Connection=False and see what happens.

Generally when I see that error it is because my connection string is incorrect or the database is down / inaccessible, but I'm sure there are other potential causes.