This is really obscure and hard to reproduce since it only occurs under unusual circumstances (as I understand it).
During the early game tutorials, the player is asked to upgrade the Church, Mage Tower, or Thief Den to unlock a tier one class. Normally this happens before the beginner town dungeons are completed and the Tavern has been unlocked.
However, it is possible to have the Tavern unlocked before this point, if the player unlocked it during the beta, but before this tutorial sequence was added to the game. In this case, the player can select the Tavern to go to the dungeon selection screen before being prompted to select a class building to unlock. The tutorial will attempt to play out to the point the player is forced to select one of the three buildings. Since the three buildings are not on screen, they cannot be selected, and the game must be restarted.
If the Tavern has been unlocked, it should be disabled during any modal, in-town tutorial sequence.