Using TinyMCE Adv 3.4.5 and WP 3.3.1, editor-style.css is not being loaded as evident in the edit page source. After some investigating this could be related to the latest WP 3.3.X upgrades...
- Disabling TinyMCE Adv plugin does not fix
- Another site running WP 3.2.1 loads editor-style.css just fine. This site also uses the same plugins although some have not been updated recently so there could be a conflict with a plugin update.
I can't be sure but I'm guessing this problem is related to WP 3.3.X upgrades or a plugin conflict.