Hi Nana
I read through all the posts and I could not follow exactly what you are doing, I am going to suggest something to check out.
When you are using the Line Tool, there are three options in the Tools panel. I had to boot up my old computer with CS5 to get the screen image yet I included it below with the line tool selected. You can see three options just to the right of the tool and they all behave differently. My bet is that you have it set on the wrong option. Here is what they do in order:
Shapes Layer: With this option, a Shape Layer is created with each line you create (probably what you want). Draw another line and you get another Layer
Paths: This does not create another Layer, just a just a new single channel in the Channels pallette. Each new line adds another path in this single new channel.
Fill Pixels: All this does is add pixels to the existing selected Layer. Each new line added just adds more pixels to the same Layer and no new Layers are created (you probably have this option selected in error).
From your description of the symptoms, this is my best guess as to what is going on. Not positive yet I think it is worth a look (fingers crossed for you
)