Problem with bone linking

Hello.

I have a problem with linking the bones to the vertices.

I’ve imported a model from MakeHuman to later export to SMD format. The problem is that when I export it all the vertices are linked to the first bone.

There seems not to be an export problem because before I’ve imported and exported a SMD model and it worked perfectly. Neither seems to be a MakeHuman problem because in Blender everything works fine.

I suppose there must be some sort of configuration in the bones or the armature, but can not find the difference between the file that works well and the one wich doesn’t.

What can be causing this problem?

Thanks.