I have 2 computers with Jaunty Jackalope on them. My screen savers are
affected by both keystroke and mouse movement.

I don't have electric sheep, I use the Pictures folder screen saver that
I have downloaded some great artworks to use.

Well I do not use screen savers but just to test it out I set one on 9.4
Jaunty Jackalope and it was not removed by mouse movement but it was by
key hit.

I just upgraded to 9.04 from 8.10 and a mouse jiggle clears the screen saver.

Your observation is exactly what I am observing Except in the case
of the Electric Sheep screensaver.
This one will not quit without a keystroke on 9.04 it does clear
with the mouse on 8.10.
Again I am asking, can anyone shed some light on this phenomenon
or offer a solution as to how to make it clear with the mouse on
Jaunty?

Have you tried the electric sheep web site?

http://electricsheep.org/

Actually I have, thats where I got the sheep in the first place.
Unable to find any answers there is what brought me to this forum, but
its beginning to appear there are no answers.