Deligates on OutlookXP/Excahnge2000

We have 6 users on our network running outlook XP and excahnge 2000.

I need to setup all the users to be able to access the boss’s calendar to schedule meetings. But on one particular user i set all the permissions to be editor and click apply & OK. But when i go back into outlook the permissions have be reset back to effectively none for all the parts (calendar, inbox etc). This problem only occurs with one user.

Any ideas?