Make sure you've got patch 1.52 installed, the ingame update system will pick up the most recent patch.
I could use more info on whether there is anything in particular that you're doing in game before it crashes. I have practically the same spec as you though, and the only thing that causes the game to hang is the wonder movies, so it might be worth you turning those off to see if that helps. To do this, open the Civ4.ini config file (a search should find it, and there's also a shortcut in Program files/Firaxis games/Sid Meier's Civilization 4), and change "nomovies" from 0 to 1. (you can just edit the file in notepad).
If that doesn't help then it must simply be a case of the game slowing to crashing point, though as I say I have the same spec as you (don't know about processor) and it doesn't occur for me. Does it make any difference what size map you play? A smaller map should work better if this is the cause of the problem. I can run a large map fine, and a huge map somewhat slowly with that spec.