It was in the fridge for two to three days, but I think I might have figured it out. I previously cooked black beans in that pot, and may not have gotten it completely clean. Considering that I started the cheese in haste while packing for camping and trying to keep my 17 month old out of everything I was doing, this is probably the issue. But don't worry, it has already been dumped down the drain. It looked really cool though.