Unfortunately, I'm not getting an error...instead of loading I just see "Adobe Digital Editions 2.0/3.0 has stopped working". Which is extremely unhelpful.
The solution I came up with on my own was to uninstall ADE 2.0 and 3.0 and download a super old version and install it. Somewhere in the forums here someone said 1.7.2 works, so that's the one I've got running now and my problem has disappeared. Since I use it only for opening the files and then transfer them to another program, I don't really care which version I'm running...
Though it is EXTREMELY irritating that the only option to open these files is ADE and it doesn't work properly and there is no support. If they're going to have a program people will need to use on a daily basis (with absolutely no other option), they need to be sure that they're there to help when things go wrong!
Glad you found a work a round. I restored to version 1.7.2 and it hasn't solved my problem which seems to do with how the connections go between ADE and where ever it's getting the book to be downloaded.