While I was able to eventually start the game on a character last night, this morning when I attempt to enter the game I get a 316712 error, which seems to be something about being unable to configure a party, despite the fact that, of course, I'm not trying to join a party.

I don't know if this is related, but as an experiment I created a different character and attempted to enter on that one. I got the same problem, and now when I attempt to switch back to the first character (going to the "Swtich Hero" option and selecting the first one) it acts as if I had not selected a different character.