It seems that whenever I have a nightmare (lucid or not) I can't scream.

I can talk and do other things but I just can't scream.

I first noticed I couldn't scream when I had that nightmare about that closet thing...I just thought that I was really scared and screamed so hard that nothing came out.
But then I noticed that in some other nightmares I had recently, I couldn't scream. They weren't really all that scary either.

Can anyone else scream or is it just me?