I'm experiencing the same issues as shown in this thread: http://forum.civicrm.org/index.php/topic,36343.0.html
Fields appear duplicated, I can't select any recipients, etc. In fact, when I select a group (autocomplete search does not work), the field label goes red as if I've missed selecting any recipients.
I've got an urgent mail to get out for this client, but can't do it through CiviMail. I've tried all versions of the layout (standard, unified, unified2 and wizard).
Joomla 2.5.28 CiviCRM 4.6.2 Browsers used: Safari 7, Chrome 42.x, Firefox Developer's Edition