This will be the shortest, yet most effective advice for those using groups in 3D modeling. Avoid using groups to form the structure of a scene.
Groups are a tool in 3D modeling that can be used for temporarily combining or separating multiple objects. I can't say why the 3ds Max engine struggles with them, but if you group several thousand objects into one, and then add more to the group, you'll end up with a slideshow in the viewport.
The only correct way to structure a scene is by using layers.