Hi there.
IMHO you are experiencing crashes and errors due to the fact that in DX9 a vertex cannot be transformed by more then 4 matrices (bones).
So you should check that none of the vertices from your skinned mesh will be influenced by more then 4 bones.
Another problem that cannot be visible from 3dsmax (which i experienced) was that when rendering a skinned mesh with DX9 some vertices were influenced by some bones which were not supposed to influence them.
I found that this problem was due to the fact that vertices were not influenced correctly (or influenced partially) by some bones. This bug cannot be visible from 3dsmax .The solutions is just to enlarge the envelopes area.


sorry for poor english