Thanks for the advice on opening and resaving. It looks like opening a corrupted file with Word and re-saving it even as an RTF eliminates the problem. I haven't tried saving as HTML yet, I have at least 100 files throwing this error so I'm looking into how to write a batch file to fix them.
When I connected the Kindle I inadvertently grabbed another book in the same series without realizing it. Sorry for the confusion.
Thanks to everyone for the help.