As an update, last weekend the Sony went totally haywire when I wasn't even using it. Started blinking between three screens - white, black, and the rotating arrows.
Googled it and found this site:
http://www.justanswer.com/e-readers/...hed-white.html
Did two rounds of resets, and it's been fine since.
My house is a hotbed of static electricity (radiator heat, dry carpets, etc). So perhaps this was building up.