I've had that with some pc before. Mine still worked. My best recommendation for you would be to really work it into a glass of milk. I suggest a clear glass so you can see any lumps that might still be in there. With the back of a spoon, smear it against the side of the glass, scrape it off, repeating till the lumps are gone. Let the glass of milk sit out overnight or 24 hours. If it becomes yogurt like in consistency, it is still active. When you go to use it for cheese, use the same procedure, but no need to let it sit out overnight. Oh, and while you are at it, that yogurt like stuff could be used as a bulk starter culture, no need to toss it!