Smaller needle perhaps?
It's called "bearding" when the batting pokes through. I think it will relax when it's off the frame and the holes will close up. You can test the theory by taking the tension off the sandwich and spritzing the backing with water. Let it dry a while and see if the batting is still poking through.
I had it happen while I was quilting once and it was like little explosions coming up through the quilt top. It would also shred my thread. I think I just got a "dirty" batt. The cotton gin mustn't have been working well the day that batt was processed. Anyway, after the quilt was off the frame & washed, you'd never know that it had been such a beast to quilt.
I just saw M.I.Late's problem child! I would not have been a happy camper! Somebody at Warm & Natural would have gotten a nastygram from me had that been my quilt!
I've got one on the frame now with a black backing and lots of black on the front but I didn't have a black batt to load at the time so I went ahead and used a Hobb's 80/20 unbleached that I had on hand with no problems.