Did you have a look at their forum?
Have a look here:
http://community.mcafee.com/forumdisplay.php?s=38586ac16a002b57eb57b991f9899e19&f=194
SiteAdvisor works as it always has on this Win98SE computer with the check marks, red Xs and such on Google searches, but does not provide the same advisories on my Win XP based machine. Both run Firefox as a browser. I use a Google search for free screen savers as a test since it has a wide variety of site ratings.
Anyone know how I can make it work properly on the Win XP?
Thanks

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic