Some mp3's do not transfer

In trying to drag and drop converted mp3’s into the clip+ some of them are not able to be transferred-I tried it on 2 groups and about 30% don’t go. At first i thought the player did not want me to be browsing and doing other things on the computer but even if i leave it alone they don’t go.

Is there a size limit on each file? 

I also have a problem with being unable to transfer flac’s because the player says it doesn’t recognize them, i thought this was a flac compatable device.

Are you sure Windows is not ‘hiding’ known file extensions? I think it’s on by default. If it is, you could be trying to transfer song.mp3.mp3 or song.flac.flac.

I’ll have to check, these are folders i’ve transfered on iriver and cowan players before. I’ve found that each player has it’s quirks and you have to figure it out. I have a lot of concert flacs and mp3’s that i would like to transfer and play in order and i hope that is possible on this player. So far the sound quality seems pretty good but i am facing a new learning curve.