Thanks very much
Ok, when I run the save with Reinforcement Logging on (which I normally have on), it does indeed freeze at 17:30:01. Basically there's just too much to log and it grinds to a near-halt executing the reinforcements code (eventually it would die, I think). I've put warnings in the tooltip of that logging option partly because it can get so big, but I think I may need to just disable that for the public build to avoid these kinds of freeze/out-of-memory problems (you aren't the first to run into it).
On the other hand, perhaps you didn't have Reinforcement Logging on? It's on the Advanced tab of the settings window, if you don't mind checking.
Anyway, when I turn off Reinforcement Logging I get a temporary freeze of a few seconds at 17:30:00, not :01, (presumably there's a fairly ridiculous amount of reinforcing going on, as you have taken a lot of territory, etc) but then it gets going again. Then it has another brief freeze at 17:30:05 (that's when the other AI player is doing its reinforcement, I bet), and then it proceeds along just fine.
... OH, now I actually read your original question carefully, and I see you weren't saying the game froze solid forever, just for 10-20 seconds. Yea, it might do that even without reinforcement logging depending on the machine.
Anyway, I'm afraid I don't have a quick fix for this (and I need to get some sleep) but I will soon be looking at making the reinforcements logic more efficient