When you’re loading a movie file onto a memory card to be used in a separate media player, OSX tends to load on a few hidden files. This usually isn’t an issue, but if the media player is a fairly dumb one it will try and play all files on a loop, this can tend to ruin the point of a loop.
This is an issue I come across a lot as if theres no control panel for the player and it’s just set to auto play through all files on the card, you’ll get an annoying ‘can’t read file’ message. You can do a few things in Terminal to delete these files, or create an Automator task to deal with them, but I’ve found a great little program called CleanEject which you just use to eject the Card (or USB key, drive, etc) and it’ll remove all files with the prefix of *.* which tend to be all the added hidden files.