I'm guessing what I recommended here didn't work.
http://www.twcenter.net/forums/showthread.php?t=330344
The cfg files has a lot of entries for hotseat mode, so you'll probably need to change these to enable it. There are two options for each setting: 'true' (enable) or 'false' (disable).
Code:
[hotseat]
scroll = false ## disable start turn scroll in hotseat campaign
turns = false ## disable forced separate human faction turns (including diplomacy) in hotseat campaign
disable_console = false ## enable cheat console in hotseat campaign.
admin_password = password ## specify password for administrator access to the dev console when console disabled. Change 'password' to a suitable password
update_ai_camera = true ## enable camera updates during ai turn in hotseat campaign
disable_papal_elections = false ## enable voting in papal elections in hotseat campaign (only first valid human faction votes)
autoresolve_battles = false ## disable forced autoresolve all battles in hotseat campaign
validate_diplomacy = false ## disable diplomacy validation for incoming propositions
save_prefs = true ## disable forced relevant hotseat options to be saved with game.
autosave = true ## autosave hotseat game at start of players turn
save_config = true ## save config file in save dir containing information about next players turn
close_after_save = false ## close medieval II directly after a hotseat autosave
gamename = hotseat_gamename ## sub directory name for hotseat save games
validate_data = true ## ensure game data files used in previous save match current campaign data files.
allow_validation_failures = false ## prevent game to load if savegame or data validations fail
If you're going to modify this file back it up first.