From what you said, it sounds like your grades include one C and two Fs with a third grade still pending. Two questions. First, did you actually fail out of the entire postbac, or are you being hyperbolic? Second, you started out well and then crashed and burned; what happened here? You don't have to post the answer on SDN, but you do need to have a good answer yourself. The postbac curriculums are designed to be intense because they are designed to mimic what medical school is like. You will have to take about 25-30 credits of science classes per semester for your first two years of medical school. Doing an "easier" post bac is not going to convince anyone that you have what it takes to handle that kind of course load. So here's what I suggest.
1) If you haven't already, sit down and think about what went wrong this past semester, and how you intend to fix that problem in the future. If it's a personal life distraction (broke up with your significant other, got treated for depression, family member died, had to work more hours, whatever), make sure that is taken care of before you even consider signing up for another class. You need to be in a mind frame where you can aim for straight As from here on out. If you were overwhelmed by the course load because of your lack of science background, then you are clearly not ready to tackle a medical school curriculum yet, and you need to spend time learning the basics to prepare yourself. If you are just dabbling in school (not studying properly, not making your classes a priority), then you should quit your program until you are ready to give your premed studies the necessary effort.
2) Once you have identified the reasons for failing this semester, talk to your advisor at the postbac program to find out what your options are. Will they let you take a LOA to resolve any personal issues? Will they allow you to remediate if your problem was lack of academic readiness? Can you change some of your Fs to incompletes and make up the work? If there is any way to stick it out with your current program, you are probably better off doing that rather than starting over somewhere else, especially if your current program is linked to a medical school.
3) If the answers to these questions are no, and you really have flunked out of the program, then I suggest you follow the first law of getting yourself out of a hole, which is to stop digging it deeper. In other words, no classes this summer. Take some time to get your life straightened out and come up with a plan to do well in a challenging science curriculum. And don't go back until you're ready and willing to do what's necessary to succeed.
