problems copying mp3 files to sd cards

I am soooo frustrated. I can put mp3 music files on cd at will, but when I try to load on an sd card I get 080070052 error code. I have tried setting up a folder on the card, but it still only takes about 3/4 of the files yet there is plenty of memory left on the card. AAAAAAAAAAAAAAAARGH! I get so damn frustrated. All my music is either originally mp3 or was converted by itunes in to mp3. I discarde the other formats because they won't let me make mp3 cds. I to understand why my sub directory folder did not work. is there a limit to how many files can be in a sub directory?