Can't access clock/calendar on start menu bar (access denied)

I have two XP users who are logging onto a windows 2000 domain as opposed to
logging on to their XP machines with a local username/password (as they used
to in the past).

Now they are complaining that they cannot double-click the time located in
the bottom right of the screen (system tray). They are getting access denied
errors.

Why is this? Do I need to set a lcoal policy for their domain username
somewhere on that machine in order to access this? It will just be a
matter of time before other users start complaining as I have been migrating
users over to domain login as opposed to local login.

Thanks,

Brad