Help with some collision stuff

So, I’ve been messing around with flash, trying to get good at some actionscripting. So I decided to try and make a little platform game to ease my way into it. I’ve been using the tutorial for Creating a Platform Game here in the Kir-Tutorials, and everythings been going great. My own problem is that the collision detections are off. So when my little guy falls to earth, he goes halfway through the ground and then stops…

http://www.geocities.com/joeboxer229/gametestz0rz.zip

Link to the .fla.

Any help would greatly be appreciated. Thanks.

PS: I know that the tutorial was in Flash MX 2004, but I had the same problem with that as I do with Flash 8.