Did you try to shut down aurora via Task-Manager while running the turm and then start again? I had something similar where Aurora got stuck and after restarting there was a "Increment Placeholder" in the log, but Aurora took up again.
I did that as well a number of times, to no avail.
Well, I tried to close the program normally. Windows 7 would tell me it's not responding and then prompt me to force-close it, which is what I did. And then when I restarted there was that increment placeholder (though it didn't say "placeholder" anywhere), but Aurora would get stuck again if I told it to process the turn.
EDIT: It seems it's not the construction cycle after all. The cycle takes place around 07:47 of May 17th, 2078, but apparently it was processed just fine (I got reports of a new officer and someone else's promotion at that time). However, I can't get much farther than that. I went on testing with smaller and smaller increments, down to 5-second ones, and found out the game can't progress after 11:32:01 or 11:32:06, May 17th, 2078. So it's probably something tiny yet critical enough to kill my game.
EDIT2: I've also noticed that the DB is growing beyond its usual size as I test further. My early May '78 backup is 80 MB, and my DB at the problematic increment is 92 MB, and it was 90 MB before the last test.