Ashley,
I'm having issues with objects with many point to define his collision boxes.
Some boxes dropped on the mountain will hit the floor and will go through it ignoring the collision box completely on the highlight area.
<img src="https://dl.dropbox.com/u/47035927/temp/collision_issue.png" border="0">https://dl.dropbox.com/u/47035927/temp/collision_issue.png
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Thanks.