Dear teekayy,

If you do not believe your grades are an accurate reflection, then you should state that. You don't want to make excuses for your performance, but focus on demonstrating how you will be a better student now. What evidence in your background supports you are different--performance in the workplace? courses since college? high GMAT score? If you do have reasons for your performance that are understandable, like personal illness, then you can state that, but rather than dwell on the reason explain how that won't affect your performance now and what in your background demonstrates you are different now.

Good luck,
Lisa