Odd. I doubt Norton would be the issue; might be worth trying an install it turned off though. And maybe whatever firewall as well (I have seen firewall issues with ADE in this forum, though not like yours).
Make sure you don't have an eReader device plugged in while trying to install. (You probably didn't anyway, but ... clutching at straws.) ADE2.0 has some very odd behaviour with some eReader devices that work fine on 1.7.2. I don't know if the problems you have seen could be related, but worth a try just in case.
Really out of ideas now though.
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Side comments: probably irrelevant but may spark an idea.
I can't remember the exact sequence I went through, but I think I upgraded v1.7.2 to v2.0 on Vista before upgrading my Vista to Windows 8.
(whatever, I quickly changed back to v1.7.2 after getting my wife an excellent Sony PRS-350 that kills ADE2.0 on overdrive books).
I don't think I even installed v1.7.2 on my Windows8, just ran the old .exe file from its old place in the previous Vista (my old Vista C drive is F on Windows8).