MediaShout will play FLV files as long as Windows has the proper codecs installed.  However, to be able to see them when selecting video files, you will need to change the file type to 'All Files'.  Then you should be able to select and play it.  If you are unable to play the files, and you get an error that they "...cannot be loaded", then you will need to install the K-Lite Mega Codec Pack.