If you are getting to turn 800 it sounds like you are playing one of the larger galaxy map sizes. If so, there are two possibilities I can think of:
1) it is crashing, but is just taking so long producing a dump file that it just appears hung. There is an immense amount of debug information that needs to be captured to allow the devs diagnose crashes on the much larger maps.
2) it is hung. The OS's "task manager" can be used to create a dump that the devs can use to diagnose the problem.
EDIT: I just thought of a third possibility: When a crash dump is produced, the OS uses the swap file, which increases the size the swap file needs to be. Have a look at the OS's "virtual storage" settings and post them here along with how much physical RAM you have.
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Other help and hints can be found in the GalCiv III General Troubles web site.