I think you have an issue with your web.config file.
Did you copy this file over or update a new version of web.config?
You may not have set the nhibernate connection string properly.
<!-- ****************** -->
<!-- CounterSoft Gemini: Database Connection String -->
<!-- ****************** -->
<connectionStrings>
<add name="Gemini" connectionString="Server=(local); Initial Catalog=MyDB; uid=sa; pwd=gemini" />
</connectionStrings>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
<!--reflection-optimizer use="false"/-->
<session-factory>
<property name="connection.connectionstringname">Gemini</property>
<property name="connection.driverclass">NHibernate.Driver.SqlClientDriver</property>
<property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property>
<property name="proxyfactory.factoryclass">NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property>
<property name="showsql">false</property>
<property name="useouterjoin">true</property>
<!--property name="adonet.batchsize">0</property-->
<!--property name="commandtimeout">60</property-->
<!--property name="defaultschema">GeminiSample.dbo</property-->
<!--property name="preparesql">true</property-->
<!--property name="connection.isolation">ReadUncommitted</property-->
<!--property name="generatestatistics">false</property-->
<property name="query.substitutions">true 1, false 0, yes 'Y', no 'N'</property>
</session-factory>
</hibernate-configuration>