Just started a mission 35, which I'm already about 60% of the way done with, and got an error message about a 'malformed response.' The game then reloaded, and is at the 'Initializing' screen, but the progress bar is remaining empty. Hope that helps.
Game bugged on me on day 24 or so. Was in the military base, had lost a barricade and my mercs for the first time. Bought the dynamite guy (who rules, btw), and on the next day had no trouble, but only a few more zombies showed up after the 'kill remaining zombies' message, and then I just stood there for a good 5 minutes waiting. This was also the first time they dropped down from above, could be related.
 "Tyrant"){kind=icon}
 "Hack Slash Crawl"){kind=icon}
 "Days 2 Die"){kind=icon}