It can take up to 24 hours for the subscription status to be updated in OneCare. Some people have reported it taking considerably longer, unfortunately.
If you renewed your subscription from within OneCare or at the Billing site, all PCs on the same LiveID will reflect the updated subscription expiration - assuming that they are communicating with the server. You can open OneCare on those PCs and click Check for Updates.
If your other 2 computers still do not reflect the updated expiration following renewal, contact support -
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve