make sure the strings folder eg thief2/strings/
doesn't contain the missflag.str file sometimes using darkloader to play fan
missions it doesn't delete
the files in the strings directory.
also check the user.cfg file and make sure non of the starting_mission lines
have the ';' missing from the front of it, eg soulforge mission in the
user.cfg file should look like this.
;Sabotage at Soulforge
;starting_mission 15
the user.cfg file is in the thief2 directory.