Are you using xserver-org 1.10.2 and the new nvidea drivers? The screensaver did not run reliably on my system until I installed the KDE test 2 iso with the updated packages. The new packages are supposed to go into the repos today from what I read on twitter. I am also using nvidea graphics.
Fully updated as of this morning from the Pass Server and all of the drivers that you mentioned
are installed I will look and see what Xserver my computer is using and get back to you .
Thanks !
EDIT:
xserver-org 1.10.2 is installed and in use