Okay, I spoke to tech support this AM.  The corruption was in the AppData directory.  So they took me to:

C:\Users\admin\AppData\Local\Intuit\Common\Authorization\v3\CefSharpBrowserCaches\protax19

where I had to delete everything.  Then I restarted ProSeries, and it allowed me to login, etc. 

One further thing -- because I had uninstalled and reinstalled first, my Home Base no longer showed all of my files, so I had to use Options to redesignate my chosen data directory, and then run Database Maintenance to repopulte my Home Base.  It was time consuming, but got the job done.

Thanks again, Lisa, for your help last night.  Even though your suggestions didn't resolve it, I sure appreciated your working with me on your own time.