OK. I've attached the IFO's for the DVD in question. I'm still puzzled how subtitles could come on 'automatically' even where there are no subtitle commands at all. I removed all subtitle commands and subtitles still were on. Perhaps the default (which is embedded somehow in the DVD or is in the firmware in the player) is to have subtitles on but these are normally 'supressed' by subtitle commands which are written as a matter of routine by commercial DVD designers.