Does anyone here use MKVToolNix (link below)? If so, does selecting "Open With..." (and selecting MKVToolNix) from within Finder actually open the file for you? For me, it just opens MKVToolNix but does not load the file. Using the "Open File" from within the tool and drag/dropping a file into the tool's window works fine.
http://www.fosshub.com/MKVToolNix.html
http://www.fosshub.com/MKVToolNix.html