1.41 problems

I'm starting to think that some reports about the game not being 'optimized' for bigger maps may be true. In any case I have 24gb of ram and a top of the line gfx card and run into similar problems (no black screen though) at around the 300+ turn mark of insane maps.

That being said I do think there are a number of things that will hopefully improve in 1.5 or 1.6. One being the sheer volume of constructors the AI builds and shuffles around the map, and currently, at least in my version, do not actually use (something is preventing the AI from upgrading its starbases with military modules). So hundreds (or thousands if you play on insane) of constructors are roaming the map bogging things down.

Hopefully the devs will turn their eyes to big maps one day, there is a lot that could be done here.

Run ccleaner I hear it works very good to counter this. More memory. You try playing with your virtual memory. Check power options it needs to be high performance. Run maintenance on your computer defragment and check disk. If for some reason you can't download Ccleaner then run clean up. The only other maintenance that is worth anything is system mechanic. So any other disk optimization programs  won't do anything. Your registry might need cleaning. Shut down some of the processes you don't need. Tweak windows for best performance why do you need windows features you can't see during the game anyways.  Lower graphics in game, and make sure that Gc3 and windows has the same resolution no reason for the game to spend extra time changing resolution. It's is important to remember that when Gc3 says high performance it means good appearance this lowers performance low performance is better. Small interface would also use less resources. I'm going to stop here hear is some simple fixes for your system. If you have a graphics card you should probably tweak it. Now if you are trying to run 100 players I would recommend cutting this down to 45. You need more ram. You could even mod for less planets. The recommendation for less than 16 gigabytes of ram is not playing maps higher than immense.

Thx, hadn't thought about changing virtual mem settings - I did install more RAM a while ago, but had still old settings for virtual mem. Now after changing those the game does work much better.