Walking with head tilted to the side

I came home tonight to find disaster after disaster in the apartment. The snake had broken out of its cage and eaten TWO, not one but TWO of my mating mice, the rabbit had knocked off his water bottle, one of my sick mice had finally kicked the bucket, blah blah blah. The worst though was when I looked in on my precious little pups.

One of my 4-week old angora pups has started walking overnight with her head tilted to the side. She has trouble figuring out which way to turn to right herself, has trouble drinking out of the water bottle, and sometimes falls to that side. This can't be anything besides a neurological disorder, could it? Could it be an ear infection or something fixable? I'm really worried about this because so far both parents and the rest of the litter had seemed really healthy and strong. This came on very quickly and I'm scared about what it implies for the breeding safety of the rest of the pups and the parents, one of whom has basically fathered all of my feeder mouse litters since none of my other males have felt like mating (except the one the snake ate, darn it!). If it is neurological, does it necessarily mean that I have to stop using the rest of the litter and the buck and doe? Should I continue breeding the parents to see who was responsible, or just cut them both out now before it gets passed on? Can it be bred out by the healthy mice? I was hoping to sell these cuties as pets, but couldn't live with myself if I sold someone a mouse that then developed the same thing.

The buck was pretty old and a red eyed white with long hair, but my best breeder; the doe was a very skittish long haired white mouse with an agouti spot on her bum, but a terrific mother. The only change I've seen in either of them is that somewhere in the past day or two the doe has started keeping one ear folded in toward her head, and the other out and healthy. Could that be related? None of the other pups are displaying any symptoms at all.

Thanks in advance, guys.