I have done a apt-get update. Afterwards I got the message: 476 packages not updated. Whats wrong?
you probably did this:

apt-get update
apt-get upgrade

which will upgrade packages on your system that do not have library or other major dependency changes.

what do you get for an output if you: (for now just look at the output and answer "n" to upgrade question)

apt-get update
apt-get dist-upgrade

Note: the dist-upgrade will have problems because of KDE files being in different places or in multiple packages, so you will have to manually deal with about 6 to 8 kde packages if you do the dist-upgrade. Check out this thread before you decide to upgrade your system:
http://www.knoppix.net/forum/viewtopic.php?p=6423#6423

the only way to upgrade 3.1 to 3.2 would be to back up your settings in /etc and backup your /home and then manually copy files from a running 3.2 system to your 3.1 hd install and then be willing to fix any problems manually.

HTH

rock