Reply to New Problem with Traktor I've not seen before?

Now, I'm still a relative noob, only had Traktor and my VCI 100 SE for about 2 months so this may be something common with a quick fix and a name but I don't know what it is?

I was playing on traktor and suddenly from the play line (in the middle of the wave form) the wave form just disappeared and I had no audio on deck A?

Also I noticed when the crossfader was on deck A it wasn't sitting still and was kind of wobbling without me touching it, not much but a couple of millimetres at least on the screen?

None of this appeared to be happening on deck B or when the crossfader was sat on the right.

I have a MBP 15, 2.56, 4gb ram with an NI Audio 2.

Any other info please let me know!!