I see there are some known issues when using ADE along with Kaspersky. See if below helps you, the text in bold is what you need to try.
If you are using Kaspersky firewall protection, you may experience download problems. This is because Kaspersky perceives Adobe Digital Editions as malware and blocks it (this can happen with the Windows® firewall as well, but it is rare). Normally when you start a new application such as Adobe Digital Editions, Kaspersky asks if you want to make it a trusted app or process, but it doesn't do this with Adobe Digital Editions. Instead, you must explicitly tell Kaspersky to add Adobe Digital Editions manually to trusted applications. The rules you need to set for Adobe Digital Editions are to "Do not scan network traffic."
If you want to try V2.0 with Windows 8, others have reported that you need to disable any popup blockers in your browser in order to do the install.
I have found v1.7.2 much more reliable for various reasons so I'd stick to it if you can resolve the issue you have with it (Kaspersky or whatever).
What is the error. Is it already downloaded ebooks you can't read; if so unlikely to be a firewall issue.
Sometimes ADE gets is registration confused and half-remembers it.
Try ctrl-shift-D to ADE to remove the old registration, then restart ADE and register again with your Adobe ID.