I've been fighting a new "feature" that I think was introduced with JB. The media volume I set while the headphones jack is in use is "remembered" as is the media volume level without using the jack. It's not that it's turning down the volume when I use the jack... The problem is that it remembers whatever the volume was set to the last time the jack was used.
Is there a way to turn this off? Something that automatically makes a change should really be controllable by the user. I'd much rather the phone just leave the volume alone unless I change it.