Got 'headers already sent ... wp-includes/pluggable.php on line 876' error (no info about where output started) after last update today.
The problem occurs to URLs without ending slash only. E.g. if I point my browser to 'mysite/blog', WP tries (I guess that) to perform redirect to 'mysit/blog/' and I see this message over the blank page. URL 'mysit/blog/' works fine. Disabled WP SEO and everything is back to normal.
WP 3.5.1, WP SEO 1.4.9