Where are you seeing that the activation is good? Do you show your subscription status as subscribed in OneCare? What is the status of your subscription when you sign in at
https://billing.microsoft.com ?
Did you remove all other security software before installing OneCare?
When you open OneCare and it shows you what actions you need to take, what does it list?
Have you checked the PC date and time - system tray clock. If it is incorrect - day, date, month, hour - fix it and reboot the PC.
With multiple problems, if the date and time are correct and your subscription status is correct, I think the most likely culprit is conflicting software, though it can also be any number of other issues. You may want to review this first:
See this post for the KB article to troubleshoot install problems - http://social.microsoft.com/forums/en-US/onecareinstallandactivate/thread/ba26b781-da18-4ce4-be8c-22647bd5d8fc/
If you are unable to resolve the issues, perhaps by reinstalling OneCare, I recommend that you contact support:
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator