b00nlander: it cycles through the modes in the mapinfo file. So if it played CTF mode last time, next time it will be 1-flag (unless people vote specifically for ctf mode).
g_forcedgamemode uses the text name: ctf, dm, 1flag, koth, pong, etc. It will only use that mode if the map supports it, though.
KiLo: just put "+set ctfmode 2" in the command line. That should fix it.