Denon DN SC 2000 4 Deck problem

Good Morning DTT Forum,

Yesterday my new Denon DN SC 2000 Controllers reached (yes two). I have not yet ordered a mixer which most likely is going to be the Numark M6 as its USB and 4 Channel but I'm still not so sure about it.
Well my actual problem is:

I can NOT use four decks on Traktor 2. The Denon's have a Deck change button with which you can control two decks per controller. Now the thing is that I can load songs onto Deck A and C on Traktor BUT only onto those, I can not acess Deck's B and D in any way. If i use one of the controllers, the other one is totally unnecessary... Though, it reacts on my actions on the other one (Led's light up the same on both and I can just use the other controller and It does the same job on A and C).

And yes, I'm using the 4 Deck .tsi mapping for Traktor.

System Information:

MacBook Pro i5 (Mac OS Snow Leopard)
2x Denon DN SC 2000
No mixer.
Traktor 2

Could my problem be caused by me not having a proper mixer?

Regards,
DJ Plutrix