I have a PC and my husband has a Mac. We are wanting to play an internet game together since he will be going out of town this weekend, but on the Mac it only gives the option for a Lan Connection or IP Connection - it does not give the option for an Internet connection like my Civ IV for PC does. Can we not play together?

I believe you should be able to use the Gamespy server system as long as you both have the latest version 1.74 patches for your Civ4 software, or version 2.13 if you want to play Warlords. I haven't tried it myself, so I'm hoping someone who has can verify this.

Make sure you have the latest updates.
Look on macgame files or similar: the 'update' that the CIV app links to in-game is only for PCs (it is a .exe I think, and PC specific)

you will then need to set up a gamespy profile for each machine
make a game with or without a password
and away you go

enjoy!

I've played against a guy on a PC (he set up the pitboss server) using Direct IP. We encountered a few Out Of Sync (OOS) errors, but since we both set our autosave to save each turn, we were able to reload and replay without incident. He set up his home computer as a pitboss server and sent me the IP address. It was really simple and we experienced only a handful of problems over the course of about 6 months of daily gameplay.

However, this was under Vanilla 1.61. Since the current version 1.74 has been enabled, I have only tried one pitboss game, with no success. I'm able to connect to his pitboss server from my work PC, but I get an error message when I connect from home on my macBook: Some of our critical files don't match the version of our host's!

Both of us are patched to 1.74, for what it's worth. Vanilla, not BtS.

In sum:
Yes, you should be able to connect. Will it be hassle free? My experience says No.

Vanilla 1.74 is pretty messed up now. The BTS 3.13 update changed some files in the vanilla folder. So there are now two versions of 1.74, the original and the one that you have if you have updated BTS to 3.13. I think that you can actually get the files that are different and update the Mac version with those.

The only vanilla and Warlords files that were changed by the BtS 3.13 update were the CvGameCoreDLL.dll files in the respective /Assets/ directories in Windows. These two files are not used on a Mac, and I don't think the Warlords one is even installed on a Mac. FWIW, the two files that bring a non-BtS Windows installation up to compatibility with the post-BtS-3.13 version are available for download here (http://gotm.civfanatics.net/civ4games/Civ4_BtS_DLLs.zip).

I've no idea whether they are checked by the cross-platform multiplayer assets check on a Mac. If the problem is an assets check failure you should get an appropriate error or warning message when you try to join a game.

At work, on a pc, the error message doesn't prevent me from connecting - the save loads and I can play my turn fine. But on the macbook, the game exits to the main menu after displaying the error message.

I wonder if there is a workaround, or some way to let the game know that it should still try and connect?