I am getting this error:

Warning: main(includes/reset_seo_cache.php) [function.main]: failed to open stream: No such file or directory in /homepages/7/d165971201/htdocs/store/admin/product.php on line 18

Warning: main() [function.include]: Failed opening 'includes/reset_seo_cache.php' for inclusion (include_path='.:/usr/local/lib/php') in /homepages/7/d165971201/htdocs/store/admin/product.php on line 18

The error appears sometimes at the top of a page. (when viewing products attributes, I click preview, then click back; the error is at the top)
Sometimes The error IS the page. (when adding a new product, I click preview, then Update; The error is then page that gets displayed.)

The odd thing is, that when I check, whatever I was doing has actually worked. e.g. products are added fine. But this error is VERY annoying, and I would love to find out what is causing it.

I am using Zencart 1.3.6