which page/code renders admin/config in drupal 7
The page that normally come up when the path is admin/config is inserted into the site by the core system module's implementation of hook_menu().

The callback function that actually produces the page is system_admin_config_page().

However, unless you (or somebody else) has hacked core (and we don't that, right?) these functions are not the cause of the problem.

Here's a link to the SOP for debugging Blank pages or "white screen of death" (WSOD).