I do not know if this is the same issue, but it is close enough that I am posting it in this thread.
Here is a save file that I have uploaded to DropBox that should allow you to recreate the issue:
Before you load the save file, launch whatever tool you use to monitor resource utilization (I use Task Manager in the detail view). When you load the save file you should be at the end of a turn (272). Look at the amount of memory being used by Galciv4.exe, it should be about 6 GB. When you hit the button to go to the next turn you should get the dialog shown below, but clicking on the "Done" button will not do anything and you will be stuck. Go to your resource monitoring software and you should see memory usage climbing steadily. Memory usage will continue to climb until you kill the GalCiv4.exe process.
Hopefully, this will help you find the bug.