I have the same problem. Wordpress 3.4.2, plugin 1.4.4.
On one hosting two blogs on Wordpress. WordPress version is the same, the same version of the plugin, the design theme is the same.
On one blog plugin works fine, the second stopped working a month ago (was a previous version)
Updating plugin - did not help, updating WordPress to 3.5 also did not help. Made a backup - still dont work it to create and edit posts and pages.
Does not open the field to edit the title, description and keywords - are not working tabs.
I am modify the class in the file admin/class-metabox.php - field unfolded, but the link "General", "Page analysis", "Advanced" not working
I read forums, see that the problem was three months ago. But I have not found the solution to this problem
Help me, please