Most likely this issue is caused by the "Always remember the user's last-used AppleShare logins" option in At Ease Setup (Workgroups). When this setting is enabled, AppleShare volumes that are specified to mount at startup will not mount at startup.
This setting is enabled by default, so many users are not aware that it is enabled. In addition, it can only be accessed throught the Security options Pane. Since the setup process does not require an administrator to change any of the Security options, users are not always aware that the option is there.
Follow these steps to disable the option.
1. Launch the At Ease Setup (Workgroups) application.
2. Click the New User button.
3. Double-click the Panels icon, whether or not you intend to provide the user with Finder access, restricted Finder access, or Panels access.
4. Click the Security Button (the button with the lock icon).
5. Click the "Always remember the user's last-used AppleShare logins" radio button to disable it.
6. Continue with the setup. If you are setting up a user with Finder access, double-click the Finder icon.