Do you get an error or does the report just not show up?
If you open OneCare, and click view last report, can you access it?
If you click Change Settings, logging tab, create support log, does that report open in the browser?
I suggest contacting support if the tune-up report won't open and rebooting the machine does not resolve it. it may be a matter of resetting the database or reinstalling, neither of which I would do just to see the fairly worthless Tune-up report.