I ran into a situation where the game freezes in a predictable, repeatable way.

Here is a link to the save file:

https://www.dropbox.com/scl/fi/ssr14cohdl72zfbm0nstf/Game-Freeze-Under-1.60.417998.GC4Sav?dl=0&rlkey=dr89cb2zbcogxmonar1x71vsh

Here are the steps to recreate the freeze after loading the save file:

1. Go to the planet named "Persson IV".  It is a planet that I just conquered during the previous turn.
2. Open the Leaders screen so that we can assign a leader to Persson IV.
3. Click on the "Governors" tab and scroll down until Persson IV is visible.
4. Scroll the "Unassigned Leaders" list down to the bottom.  The last leader should be Neil Azden.
5. Drag Neil Azden onto Persson IV to assign him as governor.
6. Exit the Leaders Screen.
7. IMMEDIATELY double-click on Persson IV to manage the planet.
8. The game should now be frozen.

At this point, TaskManager shows GalCiv4.exe using about 30% of the CPU.  The only thing I can do is choose "End task" from TaskManager.

Hopefully, you will be able to recreate the freeze and it will help you to find and fix the problem.