Ok, well, now I only get the error message when I'm displaying a page. What I'm trying to do is to have a list of the sub-pages of a particular page appear when that page is viewed. Ideally, it would appear after the content of the page -- perhaps at the bottom. However, having it appear in the loop would be good, too.
I get the same error, but just on pages. You can look here:
Notice that there is a post on the homepage, but that the About Us link is to a page. I pasted the code into the post.php exactly as it appeared in the link from above...
Suggestions? Do I have to use PHP to echo the page_id into the statement? Somehow it's just not working.