I get my blog's 404 when attempting to preview an unpublished post, and a "You don't have permission to view previews" when previewing a published post.
Setup:
My admin is at http://www.brian-fitzgerald.net/wordpress
and my blog is at http://blog.brian-fitzgerald.net
I have pretty permalinks set up
Have added the rewrite rules to .htaccess as recommended in the Settings page:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
This isn't a version problem -- situation has persisted since I migrated to a new hosting service couple years ago.
I've seen suggestions of removing the www subdomain in the site url setting of Settings > General which appears to have worked for many. Won't work for me as the subdomain is significant (blog.brian-fitzgerald.net) and I have done the ritual purging of cookies and visits from a clean browser on a clean system. Nada, nix, niente.
Be great to hear from anyone who knows what the problem is.