First check the kde version installed with for example "apt-cache policy kdelibs4"
It will return something like "Installed: 4:3.4.1-1" as with knoppix 4.0.2
The 3.4.1-1 is what you want kscreensaver to also be.
"apt-cache policy kscreensaver" will tell you the versions available. If you can't see the matching version a google might be fastest to get it.
If you do find a version in apt do "apt-get install kscreensaver=4:3.4.1-1". If you download a .deb install with "dpkg -i kscree.........deb"