I am trying to create a new portal with an existing template. But if I check "Include Files?" option and use that template during creation of the new portal I receive:

Error parsing website template the extension [.zip|.css|.template] is not allowed.

The extension in the error message changes on each try; zip, css and template are the ones I received so far. to portal gets created but does not work (gives server error)

It happens only if I check "Include Files?" option.