Multiplayer guest computer crashes frequently - what to do?

[Diesel_Train]

I've played Civ 4 multiplayer with my friend but when the game advances, his game crashes frequently and it's hard to continue the game. Sometimes his game crashes immediately after joining the game (not in the lobby but in the actual gaming screen), and the save is like corrupted.

Do you others have experienced lots of crashes in multiplayer games? I'm looking for a solution!