I got this very strange problem: whenever I want to resize images in the media library and i enter a number, the field switches to "NaN".
Screenshot : http://pix.toile-libre.org/upload/original/1360750894.png
I know that this worked.
I have deactivated all plugins and reactivated them, nothing changes.
I modified file permissions, in case there is some problem.
I replaced my wordpress files with new ones, too.
Any clues ?