MyMPx.org - Unable to Copy Songs and Videos

I am unable to Copy Songs and Videos . Whenever i put songs in my Mp4 player (2gb S1 Mp3 Player) they get copied fine but when i run them they either say "Format Error" or the player just restarts but sometimes one or two songs get copied and play fine in the player . After that when i try to play the files unreadable by the player on my computer they become corrupt . The same is with videos . I have tried putting songs and videos in different formats and bitrates but this doesnt help .