I just migrated my data from my old MacBook Pro running Snow Leopard to my new MBP running Lion. I think Mail was fine at that point, but not positive. Then I activated iCloud for the first time. Now mail opens but there is no viewer window and Mail prefferences won;t open either. HELP!!!! I have 3 mail accounts, MobileMe, gmail and AOL and nothing shows up. It still works fine on my old machine, but I get nothing on the new one.