Sorry, but the BoxCryptor Drive can either be visible for the current user only or all users on a system. It is not possible that it is visible to only your user and the SYSTEM user. If you want to access the BoxCryptor Drive from a service, you have to mount it for all users.
PS: This forum is intended to be a community forum. We try to answer as many threads as possible, but it does not always work. If you have time-critical questions I'd suggest you to submit a ticket in our helpdesk: http://support.boxcryptor.com