NHibernate unable to load Proxy Factory

I'm so stuck with trying to get a simple NHibernate app running. I'm doing "Getting started with NHibernate" step by step.
First, I got a invalid property something error (managed to fix that).

Now, I get an exception:

Unable to load type 'NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle'
during configuration of proxy factory class.

Possible causes are:
– The NHibernate.Bytecode provider assembly was not deployed.
– The typeName used to initialize the 'proxyfactory.factory_class' property of the session-factory section is not well formed.

Solution:
Confirm that your deployment folder contains one of the following assemblies:
NHibernate.ByteCode.LinFu.dll
NHibernate.ByteCode.Castle.dll"

The files mentioned are in the Bin folder, where the QuickStart.dll is.
I have no clue why this is happening!
I'm at my wits end spending hours today trying to get this to work.
The question at SO (Unable to load type ‘NHibernate.ByteCode.LinFu.ProxyFactoryFactory, NHibernate.ByteCode.LinFu’) did not help 🙁

The hibernate configuration from Web.config:

<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
    <session-factory>
        <property name="dialect">NHibernate.Dialect.MsSql2000Dialect</property>
        <property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>
        <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
        <property name="connection.connection_string">Server=(local);initial catalog=quickstart;Integrated Security=SSPI</property>
        <property name="connection.isolation">ReadCommitted</property>
        <property name="default_schema">Monitor.dbo</property>
        <property name='proxyfactory.factory_class'>NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property>
        <!-- HBM Mapping Files -->
        <mapping assembly="QuickStart"/>
    </session-factory>
</hibernate-configuration>