So I'm playing Pokemon X/Y, and got all the way to Champion Dianthe...

And I can't defeat her. More accurately, her Aurorus breaks the game. Anytime she sends it out, the game just shuts down and I get an "error: please hold down the power button to reset, tell someone if the issue persists" message. Why does this happen? Has it happened to anyone else?

The only reason I can think of is that I haven't seen an Aurorus before (never trained it up), so it's not in the dex at all. I'm training one up to see if that's the case, or if it's an issue with all Aurorus and the evolving will also break the game.