I bought a Humber Keel freighter and sent it on a long route, on which two ports were farther apart than the ship's range (50km) allowed. Instead of a single error message window I got lots of identical message windows, several pages in the message log window, all at once. I began fast-clicking them away when the game froze. It's not a deadlock, CPU usage is still at 25% five minutes later, but memory usage is dropping fast (from >1.6GB to 700MB). No useful savegame available, because it all happened in the middle of the month.
Thank you for your report. I think that I have now fixed the message spam issue. I have fixed what might be this crash, but it is difficult to be sure without having the ability to reproduce precisely the situation that you encountered.