Are you running Mac OS X 10.6 Snow Leopard? If the screensaver is not updated specifically for Snow Leopard, it will not work.
The technical reason for this is because Snow Leopard now requires that screensavers be 64-bit, as opposed to 32-bit in Mac OS X 10.5 Leopard and earlier. I was also disappointed to find that my favorite screensaver, called MatrixGL, no longer works after updating to Mac OS X 10.6. And on top of that, the developer is unknown!
It looks like your screensaver was last updated in 2008, and Snow Leopard was released just a few months ago. You could try and contact the developer to see if they are working on an update.