You need to make sure the file you downloaded is the correct , entire file. Most likely, if it is the same file size as the one you were trying to download, it is correct.

Something about your setup stopped the normal flashing process from working. My first guess is that the file download was corrupted. A lot of people downloaded files partially last night. If that isn't the cause of your problem, something else about your setup is.

If you can't figure out why your setup is causing this problem, you should probably try another computer.