I had a similar issue since I put windows 7 on one of my pcs, XP on the other one.
My friend and I are in the modern eara on a huge map and we would get OOS messages every few turns usually after a couple of random events.
I tried running civ in xp compatability mode on the windows 7 pc, this made a huge difference. We only had 1 oos in the next 4 hours and that may have been due to the slower pc acting as the host.