I reverted to
Kindle for PC 1.4.1 and upgraded the tools to 4.6, and everything seems to be working fine at this point. I noticed that when the plug-in did not work, and when I opened the book in the
Calibre Convert mode, the "input" window would only show AZW, not MOBI, as it had done previously. This seems to be a signal to me that the DRM is still in the file. Calibre would not convert these books either.
Where is a good place to get a set of instructions on stand-alone DRM removal tools, as I would like to give that a try.
Thanks.