Gloxxy

If the Mac is bound to Active Directory then it only affects the Managed users on the Mac. It won't affect the local Admin accounts on the Mac as they are not managed by Active Directory.

This only happens when a user has changed their AD password or it has been changed for them. When the user logs on for the first after changing their password a splash box appears regarding their Keychain. The options are to Continue login, Create New Keychain or Update Keychain. If you don't click Create New Keychain then the Keychain will continually ask for the Keychain password which is the users OLD password as a new keychain hasn't been created with the new password. The only way to get rid of the keychain password popup box is to delete the login keychain in the Keychain Access app. Use spotlight to search Keychain Access then right click and delete the login keychain. The Mac will be forced to create a new keychain with the new password.

So a simple reboot didn't sort this problem out? It has for me in the past. It makes it extra difficult to troubleshoot once you are running 10.9 on the Macs as the red dot has been taken out completely.

What version of OS X are you running? Does this happen after the Mac has been sleeping? I had this problem with a few Macs in our school. The NIC doesn't work properly after the Mac has been woken. I had to enable "Prevent computer from sleeping automatically when the display is off" to stop it from doing this. http://i61.tinypic.com/2kn486.png