At what point in tune-up is it currently? Scanning? If so, I suggest rebooting the PC. If it happens again, when starting the tune-up, please contact support to determine what it is stuck on.
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