Best Method of Mass Collision Checking

[thesmart1]

I'm making a platform game with multiple levels, each in its own frame. I'm adding several objects, like a solid ground, moving blocks, solid walls, and blocks that the character falls through. The objects in each levels will be different, and there will be too many objects to perform hitTests on each instance. I was also considering looping through an array that would contain instance names of all objects in a level, but that would probably lag too much (and it would be a lot of work).

So what would be a simple, fast method to check collisions with a large amount of objects?

EDIT: I've tried placing multiple objects with the same instance name and hitTesting the instance name and a moving movie clip, but it only works on the first named instance. I could put all the objects of a level in a single movie clip and do hitTests with a shapeFlag on that. Would that be the best method, or is there a better way to do this?