This is totally off the wall but since the software is free, I thought it might be appropriate to check here.
Yesterday I got a free Kindle book from Amazon. When I downloaded it, I had a few problems (normal problems based on an earlier upgrade). I started my Kindle for PC software to get the book. I was notified that there was an upgrade to 1.4.1. I took it. As soon as the upgrade happened and the software loaded again, I was told there was an upgrade to 1.6.1. That was strange but I said yes and spent hours with problems - even with Kindle Support.
If you have Kindle for PC, I do not encourage you to upgrade unless you have a Kindle for PC Installer on your PC for an earlier version or you use Chrome or Safari and can use the new Cloud Kindle. My experience is it does not work!
With the update, I get the splash screen and Windows immediately says there is a problem and closes the program. Oddly enough, it does not put the application files in a "Kindle for PC" folder, it puts it in a Kindle folder. The install does sometimes create a "Kindle for PC" folder but leaves it empty!
If you don't have Kindle for PC, I do encourage you to try it just to see if it works. It looks like the build they have created is trying to get the Kindle for Kindle to work on the PC and Windows is not happy.
Please, if you do try this version and it does not work, send Amazon Kindle Support an email to that effect. Tell them what you did and what happened. Emphasize that it is a KNOWN problem. After last night, they know about it, THAT I can guarantee!
As a result of all my attempts, I had to re-download 37 books (my non Amazon Kindle books were not affected) and have to use a much older version than I had when this first happened. I also lost all my bookmarks for the books started. That was because I tried using Revo Uninstaller just to see if the problem was a flaky registry entry.
I think the reason for the double update message is I got upgraded to 1.4.1 and right after I did that, they replaced the download version with 1.6.1. I may have been the first person to even try the new released version! The dates on the application files are 7/19/11 and that confused me at first. They may have made the files last month but not completed the build (incorrectly) until yesterday.
I would welcome any comment or any ideas of what we could have tried (myself and two different techs - level one and two).