I find this interesting because I took the same exam yesterday (9/3) and made a D. I've never failed anything. I knew that information, did well on the practice exams and still failed it. I've asked for my exam to be hand scored because there is no way that I made a 50. Even if I had not studied at all, I would have made better than that.
This is scary - I've read a couple of people who said they did well on the practice exams and then failed. If the practice exams aren't helpful for this exam they need to look at that. This is my next exam and it kind of freaks me out a little.