The Core 2 Quad is an extremely old CPU line; nearly 7 years have passed since the Q8200's initial release! This is indeed ancient; your PC may very well be too weak to properly handle an Insane sized map.

The Core 2 Quad is not equal to an i5 CPU; you do not meet the recommend specs. That being said the behavior you are experiencing is weird and does merit investigation.

Is there a dangerously insane map size!?!

also, those requirements aren't for insane maps. God knows what you need for them, as the requirments would likely be double what it is for a constantly stable game. The maps really are insane and iirc, Stardock has said play it if you can but no guarantees.

Forgive the post doubling, but there was a major change in performance.  Came back after dinner and started playing.  Three hours later, still no lagging in performance.  HOWEVER, for the first time, I had a CTD... sort of.  The game screen disappeared and I was looking at my monitor's wallpaper.  The music was still playing, but there wasn't a minimized program icon on the task bar.  In fact, there wasn't a task bar.  So I did an Alt-Ctrl-Del to bring up Task Manager, the game was still running.  Closed TM and there the task bar was back with the GC3 minimized icon.  Clicked on that and that brought back the music, but an entirely black screen.  Nothing I could do would cycle back to the game screen.  Like looking off into space, but with no stars.

Now I'm totally confused .  I haven't a clue as to what causes this kind of thing.  I'll run an antivirus scan and malware zapper tonight, but I suspect both of those won't find anything.

I've discussed this on a couple other threads, but I'm coming back to this one.  I think I've found the culprit: Steam.

Over most of this last weekend, I was able to play for hours on end with no lagging.  Today, the lagging is back.  5-10 minutes good; 5-10 minutes of lagging.  Back and forth.  The fact that I was able to play for several hours straight with no lagging demonstrates that my PC setup IS capable of carrying the load.  (Especially since I've now revealed @85% of the Insane-sized galaxy.)  I checked my video driver, which is 353.06, and it's the same driver I've had since 5/31, before I started playing GC3.  Everything is starting to suggest an outside influence that is interfering with my PC's operations.

That's where Steam comes in.  With all of the hoopla circulating because of the new games revealed at E3, Steam has been going crazy with sales and deals.... Monday through Friday, office hours.  That annoying Steam popup you often get when exiting a game you have been playing has been changing 2-3 times a day.... Monday through Friday.  If you have a Steam account, you may have noticed that while first booting up your PC, there is a "Steam is updating" panel that runs for a minute or two.  For the most part, what is being updated is the day's Steam Sale info.  But with Sales being altered and adjusted several times a day, Steam slips into the background to update that popup you get when shutting down a game.  My theory is that when Steam is futzing around behind your program, it's competing for the active use of PC resources.  And GC3 is a VERY resource-demanding program.  And Steam is VERY selfish about sharing resources.

It's a theory anyway.  The best one I can come up with to explain why GC3 keeps fluctuating between running just fine to crawling-through-molasses lagging.

Started to play the game after 11 p.m. PDT.  As I suspected, no lagging whatsoever.  Whatever/whoever is interfering with the game during office hours.

I suspect steam doing a lot of things myself.  I havent tried it, but is there a way these days to play "offline" from steam?  I know there was a way years ago, when internet was not "reliable".

You only need steam to install and update gc3 you can then just launch the exe and should be able to close steam entirely

If you try to play GalCiv 3 while Steam is shut off, then the game wants to start Steam first before you can actually play. 

according to brad excessive and insane maps are for 16-32 gigs of ram. Imense should be fine.

I can't hook the computer to the internet. If you unhook the internet it runs in offline mode. It will check for steam, and give you an option to run in offline mode. Since you don't. Have 16 gigs of ram you should be playing immense. It helps to run low performance, since I think they mean quality not performance. Windows does not run a big enough paging file you need to customize that 24 gigs of ram.

just to clarify I meant unhook the internet before you start the game. You will have to wait for updating. After it fails at updating it will give you an option for offline mode. Also every computer I've seen automatically gives you balance power options including desktops. I recommend setting this to high performance. You can also set windows for best performance.