Byz said much of what I would have suggested. Be honest. If at all possible, point out periods in the past where you have done well in school (even if you have to use high school as an example) the board who decides these things (at least at my school) was very understanding of personal situations that make life harder. Now, if you had spent all your time partying and blowing off classes because of that, they may not be as inclined to vote in your favor. But if you are honest, I bet they will be willing to let you back on a probationary basis. Maybe you could agree to a lighter course load until you feel more comfortable back on academia and are being successful in your work.

Good luck and don't give up.