Single Pages loading with index.php instead of single.php in wordpress
I had the same problem with neither the single-CUSTOM-TYPE.php nor the single.php being rendered after clicking the single-post-link.... only index.php instead of the correct file...
What helped me was a simple change back to Standard Permalinks in "Settings" -> "Permalinks" and a restore back to "Name of the Post" (Beitragsname)....
...maybe this might help someone else as well...greetz
Pages use page.php. If your single blog posts are not using single.php, then chances are either a plugin or your theme is screwing with the query before template_redirect fires. More information on template hierarchy here: