When I login on my Ubuntu system a script will mount a truecrypt container. To decrypt the container I have of course to enter the decryption password. But Truecrypt also asks for my "administrator password". Why does Truecrypt ask for my administrator password and how can I disable this?

This is the script which runs on startup:

#!/bin/sh -e

/usr/bin/truecrypt /media/windows/data.tc /media/data

/usr/bin/dropbox start

/media/windows is a NTFS partition. /media/data is writable by the user.