Yayy!
Good news!
I just used my stock standard routine, go to
http://calibre-ebook.com/download, download the 64-bit installer package to my hard drive, and double-click it. Result: v2.2 installed without a hitch.
Thanks again to everyone who has contributed this thread, and particular thanks to Kovid, not just for this, but for all he has done over the years with this incredible product.