Well you just have broken your dev node
The correct syntax for ln is :
ln -s <SOURCE> <DESTINATION>
So if you want to link dvd to hdd you use :
# delete the old link
rm /dev/dvd
# link the file
ln -s /dev/hdd /dev/dvd
now you have to rm your broken node first :
rm /dev/hdd
and recreate it :
mknod /dev/hdd b 22 64
change permissions :
chmod 660 /dev/hdd
chown root:disk /dev/hdd