I had to help out some guys from Accenture today with the setup of content deployment for a global SharePoint 2010 Internet site. Basically the first content deployment from the Authoring to Production environment didn't send across all of the published pages. As a result, settings like 'Welcome Page' were lost. Further content deployments did not seem to help or fix what was previously broken. As SharePoint's content deployment is incremental by default (UI) I created a full content deployment job through PowerShell, but then we started seeing the error 'Unable to import folder _catalogs/masterpage/Forms/Page Layout. There is already an object with the Id
in the database from another site collection'.
I used my friend Google and found this, which helped me solve the problem.
So it seems that information about what has been deployed before is not contained within the Authoring environment, but the destination environment, and deleting the site collection and re-creating it with an empty template doesn't help. In my case I deleted the web application entirely and re-created it through script. In the article, you can also detach and re-attach the content database through Central Admin.
