The error message is: iCloud Password
Please enter your password for [Old Apple ID]
I have two iMacs, and old one and a new one that I've had only a few months. This message never appears on the new one; it appears every time I start my old iMac; it appears randomly on my Macbook Pro, and it never appears on my iPad or iPhone.
On my old iMac I signed out and then signed in with my wife's ID and password, but the problem remains. Every time I boot the computer it appears-twice. When I cancel the first one it comes up again. Cancel the second and there is no further repeat.
No I don't have backup of my data.
As for Keychain, I don't know. I don't understand keychain at all. How would I know if there was a problem there?
Is it the same prompt on my Macbook? I think so but am not 100% sure. It only comes up now and then on the Macbook.
Nothing makes sense, does it? !!