mac OS X server: client side error

on the mac OS server client side, I keep getting the following error:

"System Preferences is trying to unlock Users & Groups preferences. Type an administrator's name and password to allow this."

I can't seem to get away from this message when the client logs in. The only solution I have found was to delete the user accounts that were giving this error and creating a new account.

I was able to do this because these users were new, but if it was an old user who has data saved on their accounts I would not be able to simply delete and create new accounts.

If anyone can help find me an alternative solution for this issue or what could possibly be causing this error. I would really appreciate it.

Thanks in advance.