I've got it fixed, thanks to Caulbox.  As I suspected, it was more a Python thing than a ShaderSpider thing.  

I'd been deleting the entire Runtime/Python/Poseworks/ShaderSpider/ folder before reinstalling, but nothing else. 

I needed to delete  Runtime/Python/poserScripts/Wacros/UserDefined/ShaderSpider.py

I think the problem might be that the older version of ShaderSpider creates a file that's got a slightly different name than the new version: 

ShaderSpider .py (old)
ShaderSpider.py (new)

So reinstalling doesn't overwrite the old version.

Note to anyone having Poser Python issues: if you click on a button and nothing happens, not even an error message, check for bad path names.