The preview in the screensaver window does not animate. I can see a picture of the theme I've selected, but I only see animation when I click the preview button.
Animation is slow when the screensaver uses full screen mode.
Now it does not show a preview and I cannot restore the preview. I accidentally deleted one of the pre-built themes that came with the screensaver. I have a 3DFX Voodoo 2 accelerator card and the screensaver pauses after it has been running for some time.