I don't often watch mkv files, but just an obvious question;
You are using Media Player Classic with a codec pack such a K-lite Codec Pack right? If you have both of these it's likely that they just subbed it badly. If not I suggest you download these two things.
You can download MPC and K-lite Codec pack here in the same file (K-lite codec pack comes with it) if you don't already have them:
http://www.free-codecs.com/download/K_lite_codec_pack.htm