Character is halfway through floor...?

In my model, I have a very flat box. the bottom half seems solid… the top half doesn’t. When my character falls down, no matter how far, it goes though the top half of the floor to the bottom half. I tried convex bounding and all that, and it didn’t help. the box one won’t work, because my scene has hills.

HALP :frowning:

NVM, fixed. lock this baby up!