Mail, Contacts & Calendars crashes System Preferences; iCal and Mail also affected
Nailed it! In my case, I resolved this by deleting:


/Users/simon/Library/Preferences/MobileMeAccounts.plist
/Users/simon/Library/Preferences/MobileMeAccounts.plist.7gmTk7L
/Users/simon/Library/Preferences/MobileMeAccounts.plist.lockfile