pentor on "[Plugin: WordPress SEO by Yoast] Warning: rtrim() expects parameter 1 to be strin for formatting.php on line 1381"

Hi,

WordPress version: 3.5.1
WordPress SEO version: 1.4.7

Problem:
I get in two of my category pages the following message at the top:

Warning: rtrim() expects parameter 1 to be string, object given in /home/spanol5/public_html/blogdeespanol.com/wp-includes/formatting.php on line 1381

I've figured out the problem is the SEO plugin because when I deactivate it, the warning goes away.

The pages are:
http://www.blogdeespanol.com/category/%C2%BFcomo-sonaria-en-espanol/
http://www.blogdeespanol.com/category/%C2%BFdonde-va-vicente-ttt-in-madrid/

Please help, and thanks so much!

http://wordpress.org/extend/plugins/wordpress-seo/