I had a similar issue to some other people in this thread - was having no issues doing veteran until these guys. I had to turn the difficulty down to story, then step outside the instance and reset it for the new difficulty to take effect. Was easy enough after that.

Yeah just FYI this is the thread Bioware directed me to to give specifications about my problem, so obviously they know it exists. Everyone needs to stop pretending they know what Bioware knows; they ARE aware of this issue and they ARE attempting to fix it.