Attempted to upgrade from 5.1.4 to 5.4.4. Upgrade failed due to several database script errors. After lengthy troubleshoot session we decided to roll back using database and file system backup. Now after restoring the site from the backups we are getting the following errror... Any ideas on how to troubleshoot?

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an object.]
DotNetNuke.HttpModules.UrlRewriteModule.RewriteUrl(HttpApplication app) +5305
DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +1061
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +79
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +170




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Version Information: Microsoft .NET Framework Version:2.0.50727.4927; ASP.NET Version:2.0.50727.4927

After extensive investigation there were files that were not getting deleted on the DNN installation's file system due to permissions issues that could not be adjusted due to only FTP access. After this was taken care of there were still upgrade issues. The problem turned out to be one of the database servers at the hosting provider - it had not been upgraded like the others and was still running SQL Server 2000 which is only supported by DNN 5.1.4 and earlier. So the 5.4.4 upgrade package used failed which needed SQL Server 2005 or later.