I recently upgraded my mid 2011 Macbook Air from Lion to Mountain Lion. Ever since I did this I have noticed that after sleeping for 30+ minutes the screen flashes blue twice before going to my login screen each time I wake the computer. I don't notice this any other time than when waking the computer, and it does not do this when sleeping for short periods of time. I was wondering if anyone else has experienced this? I just hope there is nothing wrong with the display and it is indeed a Mountain Lion issue, I never had this problem with Lion. If it doesn't stop or I cannot resolve it I will take it to the Apple Store this weekend when I have time and can let go of the computer for a few days if necessary for repair.