Originally Posted by Skydog
This is caused by a bug in the Amazon software. You can work around it by going to Preferences->Output Options->MOBI output and setting the “Enable sharing of book content” option.
The only problem with this method is that it will disable "last page read" syncing -- something I do not want to lose.
You can try emailing the document to your kindle address. It does a reformat so the cover shows up and is still a personal doc but syncing may work.