I have this same problem as well, very frustrating. I also have graphic bugs from time to time, and If I see that in the middle of the floor and I save and quit and then restart the game seems to prevent an oncoming crash.  Finally, sometimes the game will crash when I quit and I have to kill it with Activity Monitor.

I love this game, but I have lost many promising runs due to crashes.

I'd also like to voice my frustration about this. I've attempted playing this game several times over years, never getting anywhere because (1) the text used to be too small to read (it's still very hard to read), (2) the gamepad support is broken and the devs refuse to fix it, and (3) the tutorial isn't updated for gamepad. I finally wanted to play this game bad enough that I got a working setup for kb+m in my current arrangement. 

Now, on my second playthrough, the game crashed when I clicked the next floor button (everything appeared normal up until that point), and I lost all of my progress for that run. I don't have the words to properly express my anger. How does this game still have so many problems years after release? Why isn't there at least an autosave feature for every floor to mitigate this bug?

Devs, please fix your game! I would really like to play it!

I have the same problem (OSX Yosemite).  Blank screen after pressing the "next level" button, can hear music but nothing else.  CPU usage is around 50% of one core.  Attached is the process stack trace sample for the app when in this stuck state.

Sample of DungeonoftheEndless.txt