I recently played Quest mode on Earth. As soon as I managed to unlock the first Teuton quest (The Battle of Magetopria), I was given the option to upgrade my custom hero.
I upgraded him, but then Wyrmsun screwed up:
The quest screen became broken, a couple of buttons have disappeared, I don't know which ones exactly, but I know all buttons for configuring the hero and the quit/return button have disappeared.
Even after I start a quest and return to this screen, it remains screwed up. Meaning I am stuck in this menu, I can't return to the main menu from the quest menu.
The only thing I can do is to forcefully exit Wyrmsun or exit it from within the game. After restarting Wyrmsun, the menu is okay again.
Still, this is a serious bug IMO. I hope I have given you enough information to fix this.
Seen in Wyrmsun version 2.2.1 on GNU/Linux.