Wavemaker, I am running kubuntu feisty, and you can configure the screensavers by right-clicking on the desktop and choosing Configure desktop...
From there, in the selection on the left, choose the screensaver option. One thing to make sure of is whether or not the checkbox 'Start Automatically' is checked, and set the time to deploy. It does work for me.
I don't have experience with 3D acceleration, so I can't be of help there.