'Page not found' error when rendering node teaser or node body

I've found that this problem occurs when I try to set the rendering option for children nodes (in the module's Display Settings) to display the node teaser or body instead of the node title. Similarly, if I try to insert the theme_relativity_show_children function into the node type's tpl file, the same error is produced.

Let me know if additional information about my installation is needed in order to reproduce this error.