After some searching I found a .mkv file, it seems I can matroska files on the kaffeine package I built for VL 5.8 . However, there are a lot of different possible codecs that can be used in matroska files, and I didn't find one that has an avc1 video stream. If other matroska files play fine ( http://www.matroska.org/samples/index.html
), it's probably some missing codec thing.
Kaffeine uses the xine engine, try playing it in xine and see if that works. If the results are the same, the xine-lib package might be what's causing trouble. Perhaps a newer xine-lib will do the trick in that case.