Check the PC date and time, just to be sure, but I think that the database may have gotten mixed up. Did you change the schedule after you ran the Tune-up to completion? Did it complete successfully or was it canceled before completion?
If you didn't change the schedule, which can cause odd things with the next run time, and you did not cancel Tune-up, and the date and time are correct, with Tune-up having completed successfully, please 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 Forum Moderator