I have the same problem as well. It seems to be limited to user accounts that have “Disable the visual editor when writing” checked.
I worked around it with CSS and a custom function.
Add to functions.php:
add_action('admin_enqueue_scripts', 'admin_style');
function admin_style() {
wp_enqueue_style('admin-styles', get_template_directory_uri() . '/_css/wp-admin.css');
}
Add to a new CSS file in your theme:
.js .tmce-active .wp-editor-area[class] {
color: #000;
}
I don’t know if that causes any other issues, but it fixed the problem for me for now.
Aha! WordPress pushed a bug.
If you are getting a nag message saying that you aren’t upgraded, even though you just did, it’s not you, it’s WordPress! The 3.0.4 version thinks that it’s version 2.8.5 and that’s what’s causing the upgrade message.
Go into wp-includes/version.php and change the line
$wp_version = '2.8.5';
to
$wp_version = '3.0.4';
Problem solved!