I've tried using the plain Dannon yogurt for a starter and now I bought one of the youghurt dried culture packs & followed the directions exactly (heat milk to 180 degrees, cool milk to 112, add starter, incubate for at least 5 hours). I even let it sit in the cooler overnight (12 hours) and I still get runny yogurt. Not like runny stuff you get in the store, but like runny just barely thicker than milk. It TASTES like yogurt, but what the heak am I doing wrong???