If you starting it from here then it should be started as root.
I think it is being auto started from
-rwxrwxrwx 1 root root 2357 2012-06-19 23:05 /etc/init.d/motion
This should also be world writeable.
ls -ld /media/d9a465a2-df61-429d-9494-f76a12aa69f4/motion
3 root root 499712 2012-07-01 16:32 /media/d9a465a2-df61-429d-9494-f76a12aa69f4/motion
Can we test some thing. After it has booted up and when motion is not running, open a terminal and type
Does it start ?
sudo /etc/init.d/motion start
If it does then stop it with
sudo /etc/init.d/motion stop
Does that start motion ?
sudo service motion start
If it does then type
Post back resullts.
sudo service motion stop