Therea re many many things that can cause a batch of yogurt not to work....as you mentioned...too hot milk that kills the yogurt bugs and also too cool a setting temp that can allow other bacteria to grow, or any other "germs" introduced into the batch.
Years ago I had similar results....first batch great and then couldn't do it again....
someone suggested cleanliness of everythin g which touches the mix....and I discovered that I couldn't use a beater to mix....as the area where the blades come together just wasn't clean enough.
So...what seems likely to me is that either you contaminated the new batch with either dirty something...like did you stir with a wooden spoon or one of those silicone things that slips onto a wooden handle?
Or the temperature wasn't as right as you thought.
Try again and use only stainless things.
Linda C

Hmmmm. I've found that temperature is the most critical component, and I always add the dry milk, it makes a thicker yogurt, especially when using low fat milk. (I usually use skim, because that's what I have on hand).

I heat the milk in my big Calphalon pan, it's not stainless. I stir with whatever spoon or utensil I grab out of my countertop holder and I pour it into quart canning jars that I've set in the sink because I always slop it.

I usually dip the hot milk out of the pan with a coffee cup that I grab out of the cupboard, and I use my plastic canning funnel to pour it into the jars, so if there is any chance for contamination, mine's been contaminated!

So, I'm thinking that either your milk was a bit too hot when you started or the temperature was a little too hot or too cool while the yogurt was "working". I'm only assuming that you did add the dry milk, because you were using 2% milk?

I always make sure I use a good amount of my prior batch of yogurt to make sure I have enough starter and I always use the dry milk because I want it thick but I want it low fat.

It must just be dumb luck because I've made a lot of batches of yogurt and I've only had one fail to thicken. I've used the dehydrator to keep the stuff warm, I've used a cooler with hot water, it's all been good. The only failure I had was when my starter was getting old.

I always use the last of the present batch to start the next batch and eventually it got thinner and thinner (and sourer and sourer, LOL), until I gave it up and bought a new container of yogurt as a starter. Now I'm back to yogurt so thick it'll mound on a spoon, like the picture on the WFD thread.

It is kind of a science, though, Glenda, so I can only say for sure to try again. Not much help, I guess. Oh,and don't scorch the milk, that's my trick...

Annie

Oh I lost my yogurt mojo last year; still have no ideas what had happened to me and my yogurt during those couple of months. Both Linda and Annie are right, there are so many things that could go wrong. And yea, I usually add powdered milk if I use low fat or skim milk. All I can say is to keep trying until you get it. Don't give up!

Al

Thanks everyone. I did use some dry milk--1/2 cup to 2 quarts milk. Anyway, maybe I can use it for smoothies. I won't give up. Nothing makes me madder than not doing something because I don't know how!

I'll let you know how the next batch turns out.

Gloria