screen stopped updating - what setting affects this?

thinking something may have gotten tweaked by someone here. the canvas
screen is no longer updating when navigating the timeline. it works fine
for playback but when scrubbing or using arrow keys it does not update.
actually, if i open the project fresh, it works correctly, but as soon as i've
done any playback, however short, the updating ceases. what is the setting
that would reset this? the viewer window is not exhibiting this behavior.
(fcp v5.1.4)

thanks,
BabaG

I'd suggest a good old fashioned preference trashing Baba

that did it. thanks.

BabaG