Open Internet Explorer.
Click Tools/Internet Options
Click the Languages button
Set your language to be English- (Australia) EN-AU
Delete cookies and temporary Internet files.
Close IE
Open OneCare and click subscribe.
Login.
Payment form should now reflect the correct locale.
If not, please contact support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve