Can't use external screen ONLY a MacBook with the lid OPEN.

Hi everyone,

I just upgraded my MacBook ( first Core2Duo edition ) from Snow Leopard to Lion. Everything works great except for one thing. I can't use the my external screen ONLY while I have the lid of my MacBook opened.

In previous versions of Max OS X I was able to plug my MacBook to my 19" Samsung SyncMaster display using the external display only. I did this by closing the lid on my MacBook so it goes into "sleep" mode, then pressing a random key on my external Apple keyboard so it wakes up so it starts to only use the external screen.

Now what I used to do afterwards is open the lid ( the screen ) of my MacBook. I did this to give it more room for the heat to flow out produced by the processor. If I don't do this my MacBook tends to completely freeze when I'm doing processor heavy stuff ( Heavy multi-tasking, heavy flash elements, watching HD content etc. )

If I open the lid of my MacBook while running Lion, the screen of my MacBook turns on again. There doesn't seem to be an option to keep this from happening.

Does anyone have a solution? Is there a Terminal command I could use?

Thanks,