Read this from the forum
http://reviews.cnet.com/5208-6132-0.html?forumID=32&threadID=1313&start=0
After you are up and running again, and you have have installed SpyBot, go into the tools settings and lock your home page.
I have this problem also , for several days I have the home page I want then all of a sudden it switches ,without me changing it . when I go to internet options to change it back sometimes it takes 2 or 3 times to get it to work .
WHY Does This Happen

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic