Exactly - that’s what I’m trying to say. But since you have a clean Windows installation as you stated and you are the only one to report this issue, it is most probably a faulty Win installation on your system or a faulty download on your side.
Avast 6 is not broken by design - if that were so, you couldn’t even reach this forum because of heavy user traffic due to complaints. This version was officially released yesterday, so several millions of users have already downloaded and installed it.