Can't update to ADE4.5.1

I am running Windows 7 on a laptop and while starting Adobe Digital Editions, as I have done without problems for over a year, a popup advised me to update to version 4.5.1.  Upon clicking the button, the installer was downloaded. I ran the installer, and it first deleted the ADE folder, then asked me to sign the user agreement. When I did so, the download started, but after less than 10 seconds a popup stated "Unfortunately Adobe Digital 4.5.1 has stopped."  The program closed without any other options and so I went to the Adobe website to download it, with the same results. I tried rebooting my computer and tried again, and have tried downloading several times, always with the same result. Can anyone tell me why?