"Fades" as in the screen sleeps? Is it always at 80%?
What are the power settings for the monitor/screensaver?
I think that you will do best by contacting support to have this investigated.
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