Had the same problem in 3dsmax 2013 . Problem was, that meshes' pivots were at the same position on the 3dsmax scene, seems like babylonjs determines mesh's position by the position of it's pivot. Tried selecting the meshes and centering the pivot to object and re-exporting them, but this didn't solve the problem.
Solution: select and export meshes ( as OBJ file for ex.) and then re-import them, in the import dialog check "Center Pivots" ( top right corner ) , after the meshes have pivots centered, export them with babylonjs exporter.
Hope this helps anyone.