Greetings from Guelph.
I have been using Linux for a year now (Knoppix 4.0.1 live cd, then Kanotix hd install and OpenSUSE) and decided to take the plunge and install Knoppix to my HD.
I found that when I tried to open a hardware device like a cd writer or a dvd writer the system said it was missing HAl (Hardware Abstraction Layer), even though I verified it was installed and running, it was just not being detected by the dbus program.
To fix this try the following:
apt-get update && apt-get upgrade and then, after that finishes,
apt-get dist upgrade.
Then apt-get remove hal dbus and when that finishes do
apt-get install hal dbus.
Now they communicate and all hardware devices such as cd and dvd drives can be accessed.
I actually saw this advice somewhere else on the forum but I cannot find it again, but thank you for recommending it whoever you are!
Good luck!