Regarding the error message that you are getting you can try following steps:
1) Open Adobe Digital Editions.
2) Press Ctrl+Shift+D key of your Keyboard and deauthorize Digital Editions.
3) Uninstall Adobe Digital Editions from your computer.
Click start>>Control Panel>>Programs>>Programs and features.
Select Adobe Digital Editions from the list and Delete.
4) Also delete following files.
Type "regedit" in the box and hit enter.
Locate the following key "HKEY_CURRENT_USER>Software>Adobe>Digital Editions"
delete the full folder (Right click on it and click delete).
Also locate HKEY_CURRENT_USER>Software>Adobe>Adept
Delete the full folder.
5) Now open Internet explorer. go to Tools>>Internet options>>Connections>>Lan settings. Check the “automatically detect settings” box and uncheck all the other boxes.
6) Now download and install Adobe Digital Editions from the link given below.
7) When asked to authorize computer then please enter same Adobe ID and password which you were using earlier.
8) Now try to open the books.
I hope this will help you !!!
Set 2 is impossible with this error and after having done all steps, the error is still there.
I'm no professional, but here's how I got this error to go away on my PC using Windows 7.
I went to control panel, system and security, windows firewall.
I clicked on "Allow a program or feature through Windows Firewall", clicked "Allow another program", and selected digital editions.
Then, I went into advanced settings, clicked inbound rules, clicked adobe digital editions, and selected properties.
In the pop-up, I went to advanced and changed the edge traversal setting to defer to user.
I have no idea how or why this worked, because I don't really know what edge traversal is. It did not work after allowing the program through the firewall, only after I changed the advanced settings.
I tried this and only adding Digital Editions to my Firewall list of exceptions was enough for me. thank you