I have the same problem currently with some raw milk that I have left out to try to make whey. This is the fifth day it's been sitting out, and yesterday, suspecting that it was just too cold in the apartment, I moved it to be on top of a heating vent. I put some beet kvass there, too, but now I'm worried they both may have gotten too hot. My beet kvass was not getting fizzy at all, even after leaving it out on the counter for more than a week.
I wish Nourishing Traditions was a lot more specific about how the milk should look when it separates, and what temperatures are necessary for this work. Mine still looks like milk with the cream congealing on top, but the cream is starting to look a little more crusty and yellowish. (Yum, I know...)
Another blog I found online had some people posting that this happened to them, and they scooped the yellowish part off, and still successfully strained the rest into whey and cream cheese.
If anyone else has anything additional to add to the subject, I'd appreciate reading about it.