Woops! ... I should have read your message earlier. I went through the process of uninstalling and re-installing ZA Extreme 10, but did not use the IE cleaner. That step might be the key. Just for the record, the re-install this evening was successful, but the Site Check button was still disabled.
I will try your suggestion and run the IE cleaner when I do the uninstall/reinstall again. I'll do this later this week. Thanks for that tip.
I see others are having the same problems. Just wondering if it's just Win 7 x64 users having this problem?