MacBook Pro problems with sleeping I have two screens.  I have a MacBook Pro and just installed Mountain Lion. When I close the lid, instead of completely sleeping, it simply moves what I'm doing to the secondary screen.  Please explain?
After Lion, closing the lid puts the machine straight into clamshell mode rather than putting it to sleep, if an external display is connected and the laptop is connected to AC power. I'm not aware of any way to change this.

See Apple's page on clamshell mode behaviour, comparing 10.6.8 and Lion: http://support.apple.com/kb/HT3131