http://blogs.msdn.com/lukaszp/archive/2009/05/08/internalcatalogexception-assert-or-nullreferenceexception-when-using-a-custom-security-extension.aspxWe have seen multiple customers with issues when customizing the Security Extension Sample ( 2005 , 2008 ) that is available on http://www.codeplex.com/ . This is the sample that demonstrates how to create a Forms Authentication solution with SQL Serveren-USCommunityServer 2.1 SP1 (Build: 61025.2)http://blogs.msdn.com/lukaszp/archive/2009/05/08/internalcatalogexception-assert-or-nullreferenceexception-when-using-a-custom-security-extension.aspx#9597806Sat, 09 May 2009 00:14:17 GMT91d46819-8472-40ad-a661-2c78acb4018c:9597806InternalCatalogException, ASSERT, or NullReferenceException when using a Custom Security Extension | Microsoft Share Point<p>PingBack from <a rel="nofollow" target="_new" href="http://microsoft-sharepoint.simplynetdev.com/internalcatalogexception-assert-or-nullreferenceexception-when-using-a-custom-security-extension/">http://microsoft-sharepoint.simplynetdev.com/internalcatalogexception-assert-or-nullreferenceexception-when-using-a-custom-security-extension/</a></p>