Numark M1usb + Traktor = ??

Hi everybody,

I've got somewhat a newbie question but seems that I cannot figure it out myself.
First of all, I'm totally new to DJ'ing. I mean I know some basics and I'm somewhat familiar with sound production using a PC but I've never really played and DJ hardware/software is new for me.

So, I've got a Numark M1usb mixer that which I intended to use literally as a mixer between a TT and laptop (maybe not a best solution but I got it dirt cheap and it sounds quite good for its price), but curiosity made me to try it with Traktor and here's the problem. As it's 2 sound cards are separated, I had to use ASIO4ALL (as I'm running Windows). I've configured Traktor to use External routing and Numark's outputs for decks A and B. Then I threw a couple of tracks into decks and hit play. But what I got is a terrible glitches for both decks. These glitches occur with regular timing and it's frequency depends on Buffer size set in ASIO4ALL settings. It disappears only if I disable one of Numark's sound cards in ASIO4ALL settings.
I've tried different USB ports on my laptop, but it doesn't make any difference. Neither do checking or unchecking "multi-core processing" option in Traktor.

Does anyone know what it can be or had similar problem?

thanks,
Max