My single pages and posts aren't being loaded by single.php, rather they're being loaded in index.php

I am unable to determine the reason behind this. My is really a template which i've made myself and also the loop in index.php is nearly exactly the same within the default theme of wordpress 3. This really is creating plenty of troubles for me personally. What is the potential reasons?

Pages use page.php. In case your single blogs aren't using single.php, then odds are whether wordpress plugin or perhaps your theme is messing using the query before template_redirect fires. A lot of template hierarchy here:

http://codex.wordpress.org/Template_Hierarchy