What recipe are you using? I've never had a cheesecake fall in on itself and I make some pretty tall ones! Without the recipe, my guess is because you're taking it out before it's done. On recipes for baking, the time given is just a "suggestion" most of the time, as every oven slightly varies on temperature etc. Cheesecake is done when it's very slightly spongy in the middle.
Also if you overbeat the batter mixture it will end up falling. Only mix it enough to incorporate all the ingredients, no longer than that. It basically adds too much air to the cake so when it cools, it "deflates". Also if you open the oven to check on it, that can cause it to fall too.
This site might be helpful for you too whatscookingamerica.net/Cake/cheesecaketip
Edited by: YOJULEZ at: 11/11/2012 (21:58)