Media library not being cloned in multisite install

After successfully cloning several instances of this site, today the media library would not clone, its log was returning forbidden messages and the blog error logs was showing errors.

I finally figured out a way to make it accept the cloned site: when I cloned a site & called it test4wpmu, all the files copied over just fine, but I was able to edit the settings of the site afterward and rename it and it worked! The URL is correct and all the files are there.

I wonder if the problem comes about when I try to clone a new copy of a site that has existed at some point in the past (but was consequently deleted).