We used to have 243 portals in one DNN instance.  These have been split into separate DNN instances by client.  They all still go to the same database however.

When I go to add a portal to one of the instances, it all appears to work OK until the end.  Then I get an 'Object Reference not set to an instance of an object' error.

When I look in the database all the settings for the new portal are there and they are complete when compared to an existing portal.

The portal does NOT appear in Site Management when logged in as Host and when I navigate to the portal URL I get the following error:

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.HttpModules.UrlRewrite.BasicUrlRewriter.RewriteUrl(Object sender, EventArgs e) +2391
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +91
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +164

This is also shown in the Event Log for DNN

What setting do I need to change to get this to work.  We need to add portals on a weekly basis almost and this is making things difficult to say the least.

Any help would be appreciated.