Try the following:
Make Internet Explorer the default web browser if it is not already.
Open IE7, go to Tools/Internet Options/Advanced. Click the Rest button to reset to default settings.
Close IE.
Try to activate OneCare.
If that doesn't work:
See this post for the KB article to troubleshoot install problems - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=1588602&SiteID=2
And, finally, you can contact support:
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
This isn't a password issue, but is typically caused by incorrect IE settings or conflicting security software messing with the network traffic to the Internet.
-steve