"Ready unavailable" can't start multiplayer game

Sorry if this has been covered- I looked through topics and searched, but didn't see this.

I just bought Gods and Kings a few days ago and played some single player already. All works well. However, I tried hooking up a game with my buddy tonight and got the following message when I tried to click ready:

"Ready unavailable because another player is using DLC not installed on your computer"

This is pretty odd, because we're using the same DLC. Also, I tried starting a new multiplayer game and I still get that message even before I invite him. Basically, I'm the only one in my own game (that I'm hosting), and I see the same "Ready unavailable..." message.

We played regular Civ 5 together (before the expansion) with no problem. This is a new computer though, if that matters. We double checked that we are using the same DLC, and both our games are updated automatically by steam. Also, why would I receive that message if I'm the only one in the game lobby? I'm using the same steam account I always use, and nobody else uses this computer or my Steam account. (I get the same message when trying Online, local network, and hotseat modes).

Any help would be greatly appreciated. Thanks in advance.

 

Slight correction- this problem does not occur in hotseat mode

I tried verifying cache in Steam, checked to make sure no mods were installed... still the same problem whenever i try to start up a multiplayer game (public or private).

As soon as I set the game parameters and move to the screen where i pick my civ and the other player(s) can join, I see "ready unavailable b/c another player has DLC not installed on this comp..."

 

I couldn't find a fix after several hours of trying, so I deleted and reinstalled everything. Seems to be working fine now. Odd, but at least it works now.

 

Cannot play internet multiplayer, says "Ready unavailable" can't start multiplayer game..
I can join a game but cannot host one, and I used to. No mod's exept game of the year edition, and I uninstalled everything and deleted everything.. Doesn't work..
It says that even before anyone has been invitet to join..