17" MacBook Pro to 30" HD Display issue using Mini DisplayPort to Dual-Link DVI Adaptor.

Just replaced the Western Digital hard drive on my MacBook Pro with a SSD now running Lion 10.8.2, (updating from Snow Leopard latest version).

I have a 30" HD Apple display monitor and very much love using it.

The issue.

The MacBook Pro will only allow the 30" Monitor to display its top resolution when the unit is closed, when it is open it shows either 2 screens or mirrored screens depending upon the settings, but not at the top resolution capable by the monitor.

Now, when I was using Snow Leopard on the previos hard drive, I could close the MacBook Pro and put the computer to sleep also putting the 30" Monitor to sleep, I could then wake the computer while it was closed with my external keyboard and the screen would wake showing the FULL resolution possible on the 30" Monitor.

Then I could open the lid of the MacBook Pro and the screen would stay black allowing ONLY the 30" HD Monitor to be used effectively as a desktop computer, without the complication or need to display 2 screens or mirrored screens but most importantly the fans wouldn't need to work overtime due to the MacBook Pro being closed cutting off vital ventilation through the 2 air ducts to the left and right of the keyboard.

For some reason I cannot do this with Mountain Lion, the compluter needs to be closed in order for the 30" Monitor to display top resolution, and the fans are working overtime and the unit is getting really hot.

My concern is that the MacBook Pro will overheat, the screen will be damaged as the MacBook does get exceptionally hot when running design and audio packages, even Adobe Flash sets the fans off, and lastly the computers speakers are muffled which is more of a moo point.

If anyone could shed some light or offer a solution I would be most appreciative.

My specs:

MacBook Pro 17" Mid 2009 3.06 Intel Core Duo, 8GB 1067 MHz DDR3, NVIDIA GeForce 9600M GT 512 MB, OS X 10.8.2 - connecting to an Apple 30" HD monitor with a Mini DisplayPort to Dual-Link DVI Adaptor.

Thanks

Christian Zav