mp3 files' skip in iTunes

I have this strange problem for a long time; when I start to play mp3 track in itunes (and also in VLC player) in the beginning tracks skips/pause & play for a little. It's not important even if they are CD rips or beatport downloads or soundcloud downloads. The files are not corrupt since when i start the track again it plays flawless.

There is no CPU overload or something else, even this occour when only itunes or vlc player is open.

strangely when I'm using professional dj software, there is no lag/skip/pause at all... This can be because of CoreAudio something? Is there any fix without reinstalling mac os x lion.