The number one problem might have been holding the temperature at 115 degrees. This process takes from 4 to 12 hours, and it may have set up quicker than expected and continued on in the process. If that is the case, simply shake the jar and use the culture anyway. It won't hurt a thing.

When it first turns, it is like really thick yogurt. The longer it sits, the more it separates. There will always be shredded cheese left in the bottom of the jar. That doesn't hurt anything either. My advice would be to use a cup of the culture unless its already been thrown out and see what happens. I have sometimes had to leave my starter for a few days in the fridge after it turned, due to chores and problems here on the homestead that just won't wait for me to have the time.