I see. Our sub is ASS/SSA. Might as well recommend for vobsub for future use. And how do you know if it's vob or ass/ssa?
Via the free(!!) MediaInfo:
SSA / ASS (Suzumiya, http://www.auby.no/files/video_test..._vorbis_styled_and_unstyled_subs_suzumiya.mkv ):
(I've also annotated the UTF-8 text stream. Note that this video has human-friendly names to make it easy to distinguish between the two AAS streams. I deliberately NOT annotated them as most files don't contain human-friendly, additional labels.)
VobSub: ( file: https://dl.dropbox.com/u/13100693/html/042012RetinaHDVideoPlayers/lupaus-ads-orig.mkv ):