No subtitles on Xbox 360 with MKV files

[mathew_shinoda]

I'm playing MKV and MP4 files with subtitles and they're working just fine, but some specific MKV videos don't work with subtitles, no matter what I do.
They show that {External Subtitles} thing but the subtitles still don't show. I use the 1.70.1 version with a XBox 360.
I recently formated my computer, the same files were showing subtitles before, so I guess it's some kind of codec I'm missing. Any idea of which one?

[chocolateboy]

Problem Reporting Guidelines

I guess it's some kind of codec I'm missing.

Unless you're using AviSynth, PMS doesn't use third-party codecs.

[mathew_shinoda]

I'm using MEncoder.
For some reason Shark Plugins took care of it. PMS doesn't use third-party codecs but I guess the renderer does, I don't know.
Thanks anyway, everything's working now.