I am looking for an answer to a tax question?

I was always under the impression that if someone claimed 0 exemptions on their w-4 they were then pretty much guaranteed a refund at the end of the year. This year I claimed 0 (as always) but for some reason, according to my handy-dandy 1040 booklet, I owe an additional $850. I made just over 36k and am single. Did I break into a MUCH different tax bracket this year? I could be wrong, but it also seems like the standard deduction was higher last year? Any answers would be greatly appreciated as I am quite shocked by this, being that every single other year I have always received a refund, even if only a couple hundred bucks. Thanks in advance......