Hi, Steve.
Funny to read your post, having just answered Sarah in the UK who can't subscribe because she's being directed to the US payment form. She could use your form, though the US form won't do you any good.
I'll offer the same advice to you:
1. Clear cookies and temp files from IE.
2. Verify that your LiveID profile is correct for your physical location at http://account.live.com
3. If that LiveID has a Billing account, http://billing.microsoft.com, make sure that the profile is correct for your location, too.
4. Close IE and try to activate once again.
If this doesn't work, please post back. I'll need to check with Microsoft to find out if there is a problem with the activation servers this morning (well later, for you...) that could be causing this problem.
The following should work:
Open IE and in Tools/Internet Options, verify that your language setting is correct for your country.
If it is not, click "Add" to select your language and country combination from the list.
Make that selection the default. It should appear at the top of the list.
Remove or demote other entries that are not appropriate for your country.
I also suggest that you open an email case with support to report this problem. They may already have a solution -
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
Finally, if the above doesn't work, send me an email - sboots@mvps.org - subject of "OneCare Australia" and this link in the message body: http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2901187&SiteID=2
I'll be checking email within the next few hours and will reply when I see yours.
-steve