How to lock the screen?

[Screen Locker]

I see other people have asked how to lock the screen, but any suggestions given don't work for 5.0.1. So, is it possible to lock the screen? If so, how?

One person made the suggestion at http://www.knoppix.net/forum/viewtopic.php?t=4530&highlight=

to set an account password and issue the following:

dcop kdesktop KScreensaverIface lock

But the screen doesn't lock...

Thanks!