Pagination - works in older posts, not working in brand new post, after recent upgrade x2

I am using the Simple Pagination plugin on my site. I don’t often write really long posts that require its use, so I haven’t used it in a while.

I just tried implementing it in a post, and instead of sending me to page two of the post in question, it’s sending me to the second page of the site. However, on the most recent post I implemented it in, it’s working fine.

This is the code I am using:

{summary}
{exp:pagination paginate="both"}
{body}
{extended}
{simplepaginate}
Page {current_page} of {total_pages} pages {pagination_links}
{/simplepaginate}
{/exp:pagination}

Instead of the second page taking people to something like: http://metsgrrl.com/index.php/site/comments/the-metsgrrl-citi-field-preview/P2/ (from the last post I used it on)

It is generating this link instead: http://metsgrrl.com/index.php/P2/

I have checked to make sure there are two linebreaks above and below.

It doesn’t make sense that it would be working in one post and not the other, but I am probably forgetting something I did the first time. But I have compared the code line by line and don’t see anything different.

I did recently upgrade from 1.6.1 to the most recent build and from core to full, but again, it’s working where I’ve previously used it so that doesn’t seem to be it, I don’t think.

Unfortunately I can’t leave it implemented since people are actively reading my site and the post is getting some attention (and it’s a big traffic-getting kind of post, hence the reason I want pagination on it - not to mention it’s just too long. But that’s the behavior and the code. If you can help but you want the code live to see it, I will be checking email and will gratefully implement it asap.

Thank you very much in advance.