I have been using DNN for years but have needed to upgrade until now.  I am running a 3.x version of DNN with no third party modules.  Before I upgrade to a more current version I decided to set up a Hyper-V test image and test everything out locally first.  So I:

1) set up a Win32K/IIS6.0 environment with SQL Server 2005 Standard edition,  Visual Studio 2005 complete with .Net 2.0 and ASP.Net 2.0.  
2) Copied my running production DNN site down to the image in the C:\InetPub\wwwroot directory
3) Gave the 'Network Service' account full access to this directory
4) Created a script of the production database for all tables, views, SPs, etc.,
5) Ran the script on my local SQL Server to recreate the local DNN database structure
6) Ran the Export Data wizard on the DNN database in the production SQL Server instance and exported the data to my local DNN database (note I had a lot of trouble with this until I followed all the advice I found on Google to deal with insert identity columns - but in the end I got the data across).
7) Changed the PortalAlias to "localhost"
8) Hit the DNN Home page in the browser

At this point DNN comes up locally just as it does in production.  However, any attempt to log in gives "A critical error has occurred - Object reference not set to an instance of an object".  Note it doesn't matter if I try to login or register.  In both cases I am taken to the respective Login or Registration pages, but any attempt to submit their respective forms ends in the above error.  

Note that I am using the exact same Web.config that is in production (except the SQL connection string has changed) - that is I am using the same MachineValidationKey and MachineDecryptionkey as in production - which should match my local database.  Also note that as long as I do not log in I can navigate to all my pages that have public access.  I just can't log in anymore! 

There are no errors in the Application Event Log, no errors in the SQL logs and no problems showing up in the IIS logs.  So where can I find more information about this problem?   Does DNN log it somewhere?

If anyone has seen this issue before I could really use a pointer.  I have been banging my head against this for an entire day!

Thanks,

Rod