Run disk error checking on the drive.
Right click the drive in Windows Explorer and select properties, then tools/Error Checking.
If no errors are found and the problem persists, 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|MS Security Essentials Forums Moderator ~