I have a fairly beefy system, and it seems not to be an obvious resource constraint.
I always play on Huge maps, Marathon speed.
For the first 100 turns I can generally load a game from within the game.
After that, any attemp to load a saved game from within the game results in CTD.
I have played about a dozen games this way and it _always_ happens.
System:
Windows 7 64bit
8 core Intel CPU at 2.6GHz
6 GB RAM
ATI Radeon HD 5870 w/ 4GB RAM
The last patch did not change the behavior at all. The save game files for my current game are about 3GB.
Game loads from the main menu take a while as well, ~ 30 seconds.
The same problem also happens on a completely different machine running Vista 64 and even more RAM.
This seems like a fairly easy problem to pin down. I'm also quite suprised that this seems to have escaped the testers. Don't they test with Huge maps?