i believe it is a failure in the adhesive holding the polarizing layer in place, not within the glass envelope of the screen itself. this is a problem that the 95LX and 100/200LX palmtops suffered from too, almost exclusively in regions with high humidity such as singapore.
the screen may give off a slightly unpleasant odour too.
not that this helps you too much - the standard solutions still involve disassembly, and either replacing the screen or peeling off the polarizing layer (which you then clean the adhesive from and reattach in some way).
as an experiment, you could try placing the calculator (with batteries removed) in a WARM oven for a few hours and see if there is any improvement. try around 70 to 80 degrees celsius (160 to 180 degrees fahrenheit). the theory being to drive out any moisture from said adhesive.
DO NOT do what someone once did, when they set their oven to what they thought was 180 degrees F, and it turned out to be 180 degrees C. in that case their 100LX (that had got water inside, as i recall) came out as a lump of melted plastic.
cheers,
rob :-)