Reply to 2 Midi Fighters won't work at the same time! :(

Ok so here's the situation, I have a VCI 100, regular Midi Fighter and a Custom Midi Fighter. Using a Macbook Pro with Snow Leopard, Traktor Pro (haven't upgraded to 2 yet).
Regular MF is on Channel 3, Custom on Channel 4, so I know it's not a mapping conflict.
Now, regardless of my VCI 100 being plugged in or not, I can plug in either one of the MFs individually and it will work, no problems.
The problem comes when I plug both in. Whichever is plugged in second will not send to Traktor, although it will receive (the beat pulsing LED on the Custom still pulses with both plugged in). This happens regardless of which USB port I use, whether I use a USB hub or not.

I have a slight suspicion that Traktor might be picking up both MFs as being the same device as maybe they are recognized under the same name? But I have no idea how to change that. That's really my only guess about the problem... other than that I know both MFs are in full working order, just they don't want to play with each other