I've faced a new problem after update.
I've updated wp on my two sites (in different languages) with the same Genesis themes and plugins: one update on http://www.riseday.net went okay, other on ru.riseday.net produced the warning.
I used every recommendation on this and parallel thread to fight it: disabled plugins, switched themes, and put the word "(array)" in the code as someone proposed.
Finally, the warning disappeared but a worse problem arose.
Now every post and page on my site shows only the homepage (the url remains the url of the post/page).
The archives are shown okay.
That shocked me because I didn't touch any wp files except for minor changes in post.php as proposed here http://core.trac.wordpress.org/ticket/22883
After that I reinstalled not only this file but I also several times reinstalled wp in my dashboard updates section but nothing changes.
I need your help. Please someone advise.