So I originally set up my current Apple ID with iCloud, but then when I entered the @me.com email address I wanted and it told me it was already taken I remembered that's because I already took it when MobileMe first launched! So a moment later I remembered the password and successfully signed into the old @me.com Apple ID, but when I go to System Preferences > iCloud > Manage... > View Account... and then enter my password, the window just shakes and tells me "an unknown error has occurred" and won't let me go any further! Any ideas? I'll keep my current Apple ID if I have to but I would really like to use that @me.com email address. EDIT: Never mind, I fixed it! It just took signing into MobileMe and out, then back into iCloud again to knock something loose apparently.