Help! Duplicate Mesh popping up in Object Mode

Hi guys!

I’m new to Blender, and I just got Blender 2.57.1 on my PC and I’m having some issues with it in my modelling session. I made a simple head sculpt for my future models, and used these modifiers: Subdivision and Mirror. After doing my sculpt and applying the modifiers, in Object Mode I suddenly detect another duplicate mesh that’s inside the mesh I’ve done. Is this some sort of a bug or have I done something incorrect during the modelling process? Please help.

Some additional info: I have a duo core athlon running on Win XP

Here are some pictures.

Here is the Edit Mode screen.

Now here is the Object Mode screen. Notice the mouth? That’s supposed to be hollow when its viewed in Edit Mode.