ReadyNAS 3138 continually prompts for credentials

Hello,

I am using active directory authentication. 

Users have reported that when they try to browse the ReadyNAS 3138, they are being prompted for the logon credentials which are not being accepted.

If I authenticate(provide password) again on readynas authentication tab, it works fine and users are able shares without having to enter credentials. It's ok for a day and the issue happens again.

Thanks.