Reply to Traktor Pro via CDJ400 sound glitch

Hello everyone!
I have problem with my setup
I have two pioneer cdj400 players and a pioneer djm 800 mixer. I run traktor PRO on my vaio laptop using the cdjs as outputs and midi controllers at the same time (in external mixing mode). The feature is very handy and works really good until it comes to the sound part. Sometimes i get these really heavy sound glitches that would crack in the middle of the song. Now i tried both win 7 and xp and the OS does not seem to have anything to do with it.

Anybody has any ideas what to do?
Thank you