If you get this error:

-- Runtime error: dotNet runtime exception: Index was outside the bounds of the array.

You may need to close WWMT, reopen, scrub the timeline, then re-export. This seems to be related to a bug in Max where normals are not calculated initially with a Morpher modifier.

Previous notes in WW suggested that you move the morpher modifier to the top of the stack, but this will cause problems if there is a Skin modifier.