I've noticed that if I have the following code in my theme's functions.php file:
<?php if ( function_exists('register_sidebar') ) register_sidebar(array( 'before_widget' => '<li id="%1$s" class="widget %2$s">', 'after_widget' => '</li>', 'before_title' => '', 'after_title' => '', )); ?>
then the Ajax functionality of the admin/author editing area does not work. For instance, with the above code in my functions.php file, the "Add New Category" Link shows an empty text area, let's me enter a new category, but does not automatically assign the category to the post and have it checked. If I update the the category does show up, but its not selected.
Another effect is that custom fields do not seem to be entered, until I have clicked on the "Update Post" button, then they are entered for as many times as I have clicked the button, seemingly in vain.
Any idea as to what's going on?