3DS also carries textures. At least with Studio Max 9 trial.
There are some tools in StudioMax that will result in model deformation when importing from MED, tools like "Mirror" or Splines or Line rendering. For better results, make sure you convert every geometry to "POLY" to avoid model deformations.
Well, if you're using A7's MED, in "Edit"->"Manage Skins" check "Material Setup" of a specific skin or all in this case, unfold "Alpha" tab and set the value to "100".
I really can't see nothing else that could be causing model transparency when importing. Are you setting any flag or alpha value via script ?
I've tried exporting models, fully textured with several skins, to 3DS and then import them in MED and everything works perfectly.
Have you tried another models? The ones from the template for instance? Or only the StudioMax imports become invisible?
Oh, well, wait for another reply. Maybe someone has already solve this problem.