Just manually update. It's quick and easy. If you can sideload a book using USB you can do a firmware update.
Download the right bin file for your Kindle. Plug Kindle in then drag and drop bin file into the root directory. (The place you first see when your Kindle drive connects)
Eject Kindle, Go to Menu/Settings/ Hit Menu Again and select Update your Kindle from the menu options. Sit back and wait till done.