ManagementObjectNotFoundException

Hey everyone,

Some information about my current situation:

Created a new user in AD, created a mailbox for the user. So far everything works.

I need to add a calendar she can manage, so first off i would: Get-MailboxFolderPermission <alias>:\calendar

Here is when the problems start, Exchange throws the error: ManagementObjectNotFoundException

This only happens to a select few users. Even an user made minutes after this one, with the exact same configuration doesn't have this problem.