NHibernate, Object reference(configuration) not set to an instance of an object

I have a method that is called from other methods. This method creates a configuration object and an ISessionFactory:

private static ISessionFactory sessionFactory()
    {

        Configuration myConfig = null;
        ISessionFactory mySessFac = null;
        try
        {
            myConfig = new Configuration();
            if (myConfig != null)
            {
                myConfig.Configure(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "hibernate.cfg.xml"));
                mySessFac = myConfig.BuildSessionFactory();
            }
        }
        catch (Exception e)
        {
            throw;
        }

        return mySessFac;

    }

The problem is that I get an error at myConfig.Configure(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "hibernate.cfg.xml"));

The error is:

Object reference not set to an instance of an object

Even though this is a straight forward error I have difficulties to solve it. Here is a method that uses the above method:

 public static IList<Course> RetrieveAllCourses()
    {
        IList<Course> cList = null;
        try
        {
            using (ISession mySess = sessionFactory().OpenSession())
            {
                ICriteria criteria = mySess.CreateCriteria<Course>();
                cList = criteria.List<Course>();
            }
        }
        catch (Exception e)
        {
            throw;
        }
        return cList;
    }

My hibernate.cfg.xml is set to embedded resource

    <?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
  <session-factory>
    <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>
    <property name="dialect">NHibernate.Dialect.MsSql2012Dialect</property>
    <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
    <property name="connection.connection_string">Data Source=Mnemonics;User ID=Mnmncs;Password=mnmncs;Initial Catalog=database-name;Integrated Security=true</property>
    <property name="show_sql">true</property>
    <mapping assembly="RManageSystemService"/>
  </session-factory>
</hibernate-configuration>

And the mapping file is also set to embedded resource:

    <?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="RManageSystemService"
                   namespace="RManageSystemService.orm_rman_systm">
  <class name="Course" table="dbo.Courses" lazy="false">
    <id name="CCode" column="ccode">
      <generator class="identity"/>
    </id>
    <property name="CName" column="cname"/>
    <property name="Credits" column="credits"/>
  </class>
</hibernate-mapping>

So what is the problem with my code? I would appreciate some help.