Sorry for bringing up old thread, but this problem still persists on Samsung HDTVs, including the H series, my family has (which I setup) UE40H5550 with Slovenian menu so it supports this country, but it still doesn't support Slovenian subtitle entry (wtf

) and so here we go again with the "undefined hell" and while it works on the older UE40D6750 it doesn't work always with all programs on UE40H5550, some programs the selection is not saved, it throws back to "Preferred" and so it picks the primary language (primary fallback) which i have set to Croatian. (secondary fallback set to Serbian)
The ISP/Cable provider just doesn't have anything to do, the people I speak to really don't know much, they just say they pass the signal on, but they did make changes in 2011 i uncovered some old local threads that they make the "undefined" language to be first on the list so TVs are more likely to default to the first on the list, but it's still not perfect.
I just called them right now, they just claim how it works for them, but they wouldn't really want to do much to the signal, they say they just pass on the signal they get so they have no liability, they blame the TV manufacturer, which is fine, I guess Samsung really forgot about adding this subtitle entry to the firmware for so long.