I found the datasheet for the cover glass used by the KAF-18500,
http://www.howardglass.com/pdf/s_8612_datasheet.pdf
It is made by Schott. Apparently, it was also used in the Kodak SLR/n of 2004.
kodak dcs pro sensor filter, Schott S8612, the revenge.: Kodak SLR Talk Forum: Digital Photography Review
This filter is listed as "sealed" in the KAF-18500 datasheet. I'm going to venture a guess that some solvents will eat away at the sealing, allowing the underlying salts to react to moisture and liquid.
This glass is also sold for use in screw-in filters, here is a discussion on FLICKR.
Ultraviolet Spectrum <400nm
SO- from everything that I've read about the problem on various forums, the problem is with the type of IR absorbing glass used in the KAF-18500. It is not the only sensor to use this Schott glass. I wonder how wide-spread, ie how many sensors really affected and under what situations. It sounds like Schott needs to issue cleaning instructions. I also wonder if the IR filter is annealed to the sensor, or if it can be replaced separately from the sensor. Usually this is the case.
Looks like it was cemented on the DCS SLR/n,
How to destroy a kodak dcs srl pro sensor! Not yet.: Kodak SLR Talk Forum: Digital Photography Review
and you can see the problem is with the Schott glass filter, white-spots.
So- these IR filters have been in use for a long time, and by a lot of manufacurers. I've found articles mentioning it from the 90s. All of them are not suffering from white spots, some of them are. If they were all corroding from "just age", I'd expect to be reading about a general problem. My advice- avoid wet cleaners, use a rocket blower, send in for a pro cleaning at Leica when it's bad. Myself- I've used a wet cleaner one time on each of the M9 and M Monochrom when they were a few months old, and twice on the M8. I'm not too worried.