Corrupted Files

[AngryKid]

Hello, this is the problem, i download a song from youtube, and convert it to iphone format. Everything was fine, then i got a new iphone. Meanwhile the old sock i backuped on my computer work, the new song i downloaded and converted, they do work on my computer, but when i put them on my iphone they are corrupted, in easy way they play, then they stop and skip a part and restart to play. I don't know if it's a problem with my USB port, or if they have made some trick on purpose, anybody else knows how to fix it? I notice if i try to reupload the same song sometimes it gets better, but when i redowload it the same happens. Could be also a problem with the iphone broken? But then how comes the old songs i had backuped they do work fine? Thanks.