Messages agent wants to use your confidential information stored in “” in your keychain After upgradering to Mavericks, I have been bombarded repeatedly with the following prompt:


  Messages agent wants to use your confidential information stored in “” in your keychain
  [Allow] [Always allow] [Deny]


No matter how many times each option is used, the popup appears again after a very short while (usually less than 15 seconds).

Erasing the Messages.app/iChat-related preference files from ~/Library/Preferences/ did not work.
This fixed it for me (though note the caveat at the bottom)
Open /Applications/Utilities/Keychain Access.app, search for message, which in my case came up with two keys that I deleted. This required Administrator rights, though.
iCloud still wonky though
Probably because I trashed some of my preferences. I can live with that for the time being as it is not in my face every ten seconds.