I needed to rip a sub out of an mkv file to be able to use avstodvd (the program wasn't reading the .ssa sub file). I used mkvtool and gui to extract. The program recognized the tracks but appeared to lock up after I hit the extract button. Left it alone for a minute, then received the extracted file which was empty (0 KB).

Before jumping to the "bad file" conclusion, can anyone suggest another option for ripping? I guess I could go a different route than AVStoDVD but I like the program after only a couple of times using it.