Okay, so obviously people are split on this issue. But, I would like to add something.
When you guys talk about "fixing the ugpa" you should put an asterik next to it. The reason for this is that adcoms are not stupid, they know what your grades were during the time period that you were in undergraduate. You are not going to be fooling the adcoms by increasing your undergrad gpa by taking more and more undergrad courses. They will see that, for example, during the first 120 credits (or whatever it takes to graduate) your gpa was a 3.0, or whatever it was. They will also see that you had to take 60 more credits just to budge it up to 3.3 or 3.5, or whatever.
If your gpa is that bad it is going to take many, many credits to increase it, even a little bit. This is going take a long time and is not the best investment for you as far as time or money is concerned. For starters, adcoms don't like to be appeased, they like to see candidates who have a genuine interest in medicine/science and are actively involved in the area. Advancing into graduate work will show that you have more interests in life other than trying to conform to the application, and demonstrates that you are passionate enough about science/medicine to get involved at more indepth level. Regardless, of what was argued about above, graduate work is considered "advanced work", I know this because I have spoken to many faculty about it, and they are impressed with good grades in graduate school, with or without inflation. Furthermore, if you do go back and take more undergrad courses and still don't get in, then where are you? You are back at square one. The worst cases scenario with taking grad courses, if you don't get in, is that you are now advancing towards a master's degree, which med schools do like. You won't lose the time nor the money that you would if you continue to take undergrad classes and then fail to gain acceptance.
And this discussion does not even begin to touch on the intellectual gains that you will make in grad school. Learning to be active in the cutting edge of science not only conceptually, but also experimentally, will go a long way towards making you a smarter and better doctor (those of you anti my message, please note, i am not saying it is necessary to being a good doctor). So really, the choice is a matter of how you think your time will be best spent, i.e.. grinding away at an already deficient ugrad performance, or advancing your academic career into the graduate arena. Please do not worry about the inflation/non inflation debate, it is a non issue because maybe some adcoms will factor it in, maybe some won't, it all depends, all med schools are different. But, getting A's in graduate school is never, ever taken lightly.