template-loader.php Line 6 & 7

I just went through a hectic four days involving a redirect loop in WPMU.

The issue turned out to be these two lines in the template-loader.php file (6 &7):

if ( defined('WP_USE_THEMES') && WP_USE_THEMES )
do_action('template_redirect');

I use child theming with Canvas as a basis. When the issue was going on, I loaded twenty twelve and it still produced the redirect error.

If anyone has any insight as to how what in a child theme may cause this issue, it would be greatly appreciated to know.

As always... thanks...