Lloyd, you're the second one to post this issue today. The other post was here -
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=3113990&SiteID=2
Can you tell me where you downloaded OneCare from? I assume you have a trial mode 2.0.2500.22 version according to Help/About in OneCare?
And, you are using the same LiveID to activate that you manually verified at the Billing site? (sorry for asking, when that *is* what you said...)
Normally, I'd advise that you delete your cookies and temporary Internet files in IE and then close IE and try again from within OneCare, but since you just installed after formatting the PC, I'm not sure that's needed. I'd give that a try anyway. I'm also contacting the OneCare team on this issue this evening.
-steve