Shortcodes do not appear in appropriate position in text (Wordpress version)

If some text is inserted in a page/post before the shortcode, the output of the shortcode still appears as the first thing on the page.

I have done some research into resolution and found this:
http://helpdesk.objects.com.au/wordpress/include-content-with-a-wordpress-shortcode

However, I haven't managed to get the code quite right in the wordpress.php file.