Can you save the installer to your desktop instead? If you still continue to face difficulties you can try downloading and installing version 1.7.2 from Can't install Adobe Digital Editions 1.7.2 - http://helpx.adobe.com/digital-editions/kb/cant-install-digital-editio ns.html.
You may also want to try disabling your anti-virus protection temporarily. The fact that you are facing this same difficulty in two different web browsers would seem to indicate your security software is likely interfering with the installation process.