There is no evidence that vitamin C causes kidney stones, as you can read here:

http://lpi.oregonstate.edu/f-w99/kidneystones.html

I agree that commonsense thinking is that vitamins and minerals should be taken in as natural a state as possible, but Pauling said that his research showed that plain ascorbic acid was as good as anything more expensive with bioflavonoids etc. After I'd read one of Pauling's books and did some research myself, I lost any fear I had of taking large amounts of vitamin C, and it's been enormously helpful for me.