Pressing "select" or re-selecting the visual clears up the problem (thanks for the tip about select! :) The trails aren't the random starbursts that are part of the visual. When it corrupts, every star leaves a streak from where it originates all the way to where it disappears from view. The display becomes completely washed out with streaks and you can no longer read the date and the clock (since it's only every other pixel) becomes almost unreadable.

Bruno