I haven't signed up for OneCare, but have a similar sync problem. I've had the same Hotmail account since 1999, and have not upgraded to Internet Explorer 7, and still when I try to get Outlook to sync with Hotmail I get a similar message:
Task 'Hotmail: Folder:Inbox Synchronizing headers.' reported error (0x800CCCF6) : 'The server responded 'Access to Hotmail via Outlook and Outlook Express now requires a subscription. Please sign up at http://join.msn.com/general/Email'. '
I also can't access the Hotmail Calendar online -- it just times out. What's up?