Bugs on Knoppix 3.9 (see #15): http://www.knoppix.net/wiki/Bugs/3.9-2005-05-27
A probable solution to your problem: http://www.knoppix.net/forum/viewtopic.php?t=19518
Which all gives support to the reason why many of us do not recommed a install of Knoppix to the HD http://www.knoppix.net/wiki/Hd_Install_HowTo