GAL Update

Is there any known reason that the GAL would not update for new users/mailboxes when Cached Exchange Server is enableds in Outlook 2003.

For Example: A user is added to the domain and given a mailbox. If I go into the GAL, that user is not shown. However, if I disable cached Exchange Mode, the user shows up in the GAL. I can then re-enable CEM, and the user is once more not shown. (hope this makes sense).