Any time you are using fast switching on then Mac you will have problems with external drives that are not local to the machine.

My configuration has 2 MyBook drives connected to my Time Capsule. One I wanted to use as storage for my iTunes library, and the other is currently holding all of my backed up media.

When user 1 mounts the drive a mount point is created, /Volumes/Drive. The mount point belongs to that specific user with rwx permissions. When you switch to another user, user 2, and attempt to access the drive the first time a new mount point is created /Volumes/Drive-1. This mount point has rwx permissions for user 2, but obviously not for user 1.

Finder understands this first connection to the mount point, but if you close finder and attempt to connect to the drive in something like iTunes things get messy.

I'm assuming this script could help work around this issue? The mount point needs to be owned by either root or admin, and needs to have chmod 777 applied so all users have rwx permissions.