Here is a list of the issues that caused the game to not work:
1. One player crashed after the host clicked to start the game. All other players' games got to the "Waiting for all soldiers to arrive on the battlefield" screen, which lasted until we decided to stop waiting. Regardless of the nature of this player's crash, the game will not work if one player crashes during loading.
2. We tried again without the player who had crashed. This time I was hosting. The problem was that one player joined the game AFTER I had selected the sandbox settings. When I clicked launch, he was left behind in the game room, while the rest of our games loaded to the "Waiting for all soldiers to arrive on the battlefield" screen.
3. On try three, the issues were different. This time, some players' games crashed while in the room, before I had selected the sandbox oob. This happened after we had waited in this room for about 10 minutes I think.
4. On try four, all players got in the room, I selected the sandbox settings after ALL players were in, no players joined or left after I chose the settings. I clicked launch, and it worked for all of us.

Therefore, some things to know when setting up a game:
1. ALL PLAYERS must be IN THE GAME ROOM BEFORE the host selects the sandbox settings.
2. If ONE PLAYER's game crashes during or before the loading process, all players will get stuck on the "Waiting for all soldiers to arrive on the battlefield" screen. If one player's game is crashing there's no way to start the game with him unless his issue is resolved. In our case we played without him, hopefully the issue will be resolved some time when there are no 10 players trying to get the game going.
3. Do not delay in the room. Figure out what you plan to do before creating the game, and then when you create it have all players join very quickly. After the players are in the room, select the sandbox oob, have all players choose their commanders, and then launch the game. If you wait in the room two things can go wrong: (1) another player may join which will mess the game up if you already selected the OOB, and (2) the players may start crashing.
4. We have no reason to suppose ventrilo caused any of these problems. When the game did work, all players were in ventrilo and we stayed in it throughout the game.