I have to be candid; it's going to take a lot of work
on your behalf, but it is possible.
First, you'll need to do extremely well in your post-bacc. program. The recommendation I hear in the various newsgroups and web-forums is to take upper-level premed courses and CRUSH them.This means courses like Physiology, Microbiology, Molecular Biology/Biochemistry, Anatomy, Histology.
Med schools want to know you can survive the incredible volume they throw at you. Since these are the courses you'll take in first/second year med school, doing well in them at the post-bacc level will prove you can survive.
Second, you'll have to study like mad and do extremely well in the MCAT. Since it's standardized across North America, the MCAT is the wonderful levelling device that can help you make up for a bad GPA. This means you'll have to work hard at Physics, Inorganic and Organic Chem, English comprehension and writing, and Biology/Biochemistry. Check out my website, and my Links page for further help here.
Still, even with this accomplished, there will doubtlessly be several schools which use computers to weed out applicants with low GPAs. Therefore, even though your current academics might be great, your past academic record will sink you at some of the schools you apply to. However, if you do well in your post-bacc program, and your MCAT, I think you've got a good shot at getting it. The question is whether medicine is what you really, really want. If it is, I believe you can still go out there and get in.