Computer crashes when screen saver loads

[Fraser Parlane]

I recently changed my screen saver, to latice I believe, and since then, when the screen saver comes on, the screen goes black, and the only way of recovering is to shut down. When I go to change the screen saver, the computer freezes. When I close the lid, it only locks the computer, and I can still login. Any hints? Ubuntu Jaunty Jackalope.

Fraser Parlane