"Password Missing" Enter the password for the account "iCloud"

After upgrading my iPhone 4 to iOS 6.0 and setting up as a 'new phone'...I've had this recurring problem with my iCloud mail. Despite entering my iCloud password successfully in settings as well as my Apple ID (same email/password), I continue to get prompted three times with this "password missing" message everytime I use the Mail app. It prompts me every time I'm IN the app, not necessarily launching it from closed. I have done the following:

1. verified that the password was entered correctly
2. checked my iCloud mail at iCloud.com with the same password
3. verified my apple ID and password at appleID.apple.com
4. continued to receive mail without incident on my macbook
5. Synced the phone with iTunes (leaving mail, contacts, and calendars set to iCloud sync)

Not sure what to do next. I could try wiping the phone again, but suspect I'll have the same problem. Found a similar posting on this topic last week that said going to the Manage Apple ID site was the solution. Can't find anyone with a similar problem in Communities.