I used: apt-get install linux-header-`uname -r`. The package was: hwclock 2.18. What would be the right Knoppix-specific version for 2.6.32.6? When I checked the version with dpkg, it said:

ii linux-headers-2.6.32.6 2.6.32.6-10.00.Custom

Does it mean that I have the correct Knoppix version? Probably the problem is in hwclock and not in headers.