I am unable to open "Quicktime Player Document" files. The extension is .mkv.
I can open them in VLC, but I want to open them in Quicktime so I can convert them to iPod.
The MKV file container is not nativelly supported by QuickTime. And, even if you have third-party support for the container, the data formats may or may not be compatible with your system depending on your QT codec component configuration. You might be better off opening the MKV files in the free HandBrake app and using one of the mobile device conversion presets depending on which iPod model you are targeting. Like VLC, Hadbrake contains its own built-in support for both the file container and most of its common data compression formats. The Perian codec component package and QT 7 Pro might also be a viable alternative but many Lion users are reporting configuration problems.