Some 10.8 clients do not display the network user option at login
I have a new Mac Pro Server 10.8.5, eight new Mac Minis and two iMacs for clients. Some of them display the "Other..." login option, and some do not. If I wait a few minutes, a small left pointing arrow appears next to the login/password that alows me to 'go back' (even though the machine was never there) and select "Other..." This will be an issue for the typical impatient user.
What is causing the delay on some of them? The other clients display the "Other..." option immediately.
Thank you!
Mac Pro, OS X Server