Hm. I've not seen that with anyting else than the 0.08 Beta App, but I've not been running on 10.4 lately. Some questions to further track this down:
What version of einstein are you running? Already 4.82 or still an older one?
And what did you try to quit the screensaver? It usually doesn't respond to mouse movements, you have to click or press a key.
When it doesn't go away, is the screen blank or showing the sphere? Does the sphere rotate or is frozen? Does the crosshair move over the sphere and the position pointers in the lower right corner change?
Do you have password protection enabled? Do you get the spinning wheel as a mouse cursor, an arrow or just none at all?
BM

Screensaver won't quit on Mac OSX 10.4.2
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Shouldn't be. I tried to reproduce your problem, but to no avail. I assume you are using - wait - There might be a chance for a conflict resulting in that phenomenon on the transition between 4.78 and 4.81, i.e. when one CPU is running the old and the other already running the new App version. Has this been the case?
BM
BM