Help! I have a macbook pro running lion 10.7.4. Ive just noticed that when i go to the 'purchases' tab in the app store on my macbook pro, some of my apps havent installed. If i click 'install' next to these apps, it does the timer for a second or two then stops. Why is this?! I have Microsoft Office 2011 installed, not sure if that is causing compatibility issues, if its not that then does anyone have any idea what else is causing this?!