DDJ SX2 sound stops

Hi!! i have the Pioneer DDJ SX2 (version firmware 1.05 with Traktor 2.6.8/ tsi file pioneer) and the sound stops 1 or 2 seconds.. I have MAcbook Pro with 4GB ram - 2.4ghz.

initially i used Serato but i had the same problem. 

I worked 7 nights with this controller and failed always.. 

I checked that is a common problem with others DJ´s.. how do I fix the problem?

Thanks

Filipe