Luckily I had
purchased a few sets of the lovot blocks and other parts fron the
manufacturer when I bought the windowsn(I worked for the dealer) so I
was able to replace the swollen blocks. No amount of soaking in
alcohol or any othe substance was effective in returning the block to
the proper size. No idea what kind of plastic it was- but it sure
didn't like WD-40.

I've heard of certain materials that swell in the presence of oils. Maybe it wasn't the solvent in the
WD but the mineral oil it contains. IOW, any spray with mineral oil might have had the same effect.

According to the chart at

http://www.plasticsintl.com/plastics...nce_chart.html

mineral oil has a "C" compatibility rating for polycarbonate and
polypropylene ("Moderate attack of appreciable absorption. Material
will have limited life.")

For "Lubricating oils (petroleum)" HDPE also gets a "C" rating.

For "white spirit", the plastics listed are all either "A" (no attack,
possibly slight absorption, negigible effect on mechanical properties)
or "*" (no data available).