Strange that. Could the file have become corrupted? Is there any way you can try it on something else, burn it on a disk or something and play on a standalone DVD player, at least then you would know if it was something to do with the player or the actual file. Sorry I can't be of more help but its the only thing I can think of if your other files all play ok.
Have you tried using a newly created video file to check if the same problem occurs?
What about trying a different player and seeing if that can play the whole file.....if you get issues with a alternative media player you know it's the file thats corrupt.If it plays ok then you have a problem with Media Player or the codecs in media player.
Try overwriting the standard Media Player codecs with an alternative codec pack such as K-Lite Codec Pack Standard click here