I suggest that you contact customer service on this problem. Normally, I'd suggest that your address may have been entered with characters that the form doesn't like. It hates punctuation of any type - anything other than numbers and letters makes it burp. However, that usually results in it clearing the form with no error. They may have changed that, though. Make sure that your name and address are entered with only letters and numbers. If that isn't the issue, support/customer service is the way to go.
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
Unofficial path - send me an email at sboots@mvps.org with a subject line including "OneCare" (to get past my spam filtering) and in the message body, tell me what country you are in, your forum nickname, and paste this link:
http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/44f81d96-1fa9-4584-9c22-953fb2f9bcda
I am not online 24x7, so you may be waiting for a reply, but I'll do my best to hook you up with support.
If you don't get an email response from me wthin 24 hours, post back as my email provider is getting more aggressive with the spam filtering.
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator