Cannot play .mkv files anymore, it says "Unsupported Data"

[xbt]

I can't be sure but maybe it has to do with a [relatively] recent PS3 update?

Files I used to be able to view before, I can no longer view. At first I thought maybe somehow the video files became corrupted. But then I verified their integrity and there is nothing wrong with the video files.

So how can I get .mkv files working again?