I have a Mid 2010 edition Macbook Pro running Lion and I recently noticed that it will not sleep if I close the lid or select sleep from the Apple icon if it is connected to the power adapter but it sleeps fine (using the sleep light as an indicator) while on battery power or I put it asleep on battery power and then reconnect the power adapter. Also, at times, when I open the lid (never having gone to sleep), the screen comes on and then turns off after 5-10 seconds. Any ideas?