My baby Beauty has been nothing but the perfect puppy since I got her a few weeks ago.

Now all of a sudden she is biting and I don't mean "Play" biting.

I have always been told that a dogs' teeth should not be allowed to come in direct contact with human skin and for the past 3 weeks I have been training her not to bite PERIOD. I say Ouch in a louder than usual tone and stop playing with her for a few seconds and it seemed as if she was getting the hang of it, but on several occassions today she has snapped at me and I don't know why.

She is still her normal playful self except for the biting. Can anyone tell me what I am doing wrong because I want to correct this problem before it gets any further.
Thanks