I have installed Mavericks and everything went well.
I rebooted it this morning normally.
After connecting to my session (works well so far), Mavericks asks me the password of the keychain "Local elements".
It asks me this for "Messages", "CalendarAgent", "accountsd", "AddressBookSourceSync", "com.apple.iCloudHelper.xpc", and "Keychain Agent".
I have absolutely no idea about this password and clicking on cancel doesn't change anything. Passwords keep being asked repeatedly.
Please tell me someone has an idea.