I have a deck that is in the beginners arena locked up and there is no beginners arena anymore for me to quit out of.
I have exactly the same problem. And I can't change this deck, because most of my cards doesn't meet requirements for the arena.
Although I see no developers are reading this forum, so I'm just wasting my time writing this.
Solution for decks stucked in beginner arena - http://forum.kingdomsccg.com/?q=node/30247
Thank you, TomKat. You saved my slot. Hopefully not just mine.