I accidentally performed an upgrade from Lion to ML and then started messing around with the new Safari. I rebooted my machine and it froze so I decided to reinstall ML again, only this time I was going to do a clean install. So now when I go to Safari and hit the iCloud tabs, it shows my MacBook listed twice with what I previously had open along with my current MacBook. I'm not sure how I can get rid of my old iCloud entries. It's really bugging me. Wish there was a way I can reset the iCloud tabs feature to forget what I currently have open.