I am trying this with DNN 4.3.7 and have not had success yet. Is this only for DNN 4.5.1 or above? I still get the message "... is not a valid portal template file" Any ideas? Thanks.

This is a seriously old thread, and yet I spent a couple days resolving my challenges in creating a parent portal using a template that threw the same error on DNN 6.01.03

My solution was:

Determine which pages were created before the error by looking at Host Portals and then the DB Tabs table. The last tab created contained one or more modules - or the page itself has explicit permissions set which are flagging the error.

After resetting the errant permissions (Administrator view-edit) and rerunning a NEW template created from the recently changed site, I worked through the series of pages with the permissions challenges.

Hope this helps.

PS - do lots of backups!