I came across an odd issue with the Item Editor. I was making a couch, and had named the model "MAIN" in 3ds Max 2010. No type of collision proxy would work, including the default bounding box from the item editor, or a proxy object using the "proxy" name for a submaterial. Neither OpenCollada nor Autodesk Collada would work, even while following the wiki instructions for making a proxy.
When I changed the name of the model to "box02" it worked fine. My guess is "MAIN" is a reserved word somewhere in the pipeline from 3dsMax to the item editor, but I have no idea where, or if there are other reserved words. If there are, we should make a wiki page noting what words to avoid.