Starting to look like this thread: http://www.knoppix.net/forum/viewtopic.php?t=3592
How are you going about this? K-menu -> KNOPPIX -> Configure -> Configure Printers ?
Do you see any specific error messages with: cat /var/log/cups/error_log ?
Is cups running even though it supposedly exited: ps fax|grep cups
Which version of Knoppix do you have?
Sorry for just having questions instead of answers