Mixed mode mailbox Calendar permissions

All users are logged into NT 4.0 domain DOMAINNT and their mailboxes are in a diffrent Windows 2000 AD domain DOMAINW2K. There is a 2-way trust between 2 domains (DOMAINNT and DOMAINW2K). I am having problems giving Calendar access to delegates. Here is an example:

On MANAGERONE’s mailbox, at the root level, Default=None, ASSISTANTONE=Reviwer, Anonymous=None

On the MANAGERONE’s Calendar, Default=None, ASSISTANTONE=Editor, Anonymous=None

I logged in as ASSISTANTONE to his/her outlook, setup additional mailbox as MANAGERONE, try to click on MANAGERONE’s mailbox and got a error “Unable to display the folder”

Please help.