I have a HTS5581/98 system, when playing movie from external mobile HD, i put the srt file together with the movie.
if the movie is MP4 format, i can not choose the sub-title character type, so the subtitle become un-readable. while if the movie is another format (for example MKV), i can choose sub-tile character.

I believe this is bug. Philipls, please update the firmware and solve this problem.