Hartz ultraguard flea and tick question?

Like 2 hours ago I was at target and I bought the Hartz Ultraguard Flea and Tick (16-30lbs). I didn't think to read any reviews on it and I believe I have used it in the past on my boyfriend's dog. I put it on him and everything was fine. I then Googled the product and found all of these Web sites say that their dog died or got really sick, etc. I started to freak out and gave my dog 2 separate baths to get rid of the product. Am I going nuts? Does this product really hurt animals? If so, how can they keep manufacturing this product?!?!