The user interface for this is apparently too confusing for most
users--myself included.
Go to Tools, Advanced tools, Browser Hijack (whoops--can't look at the UI,
'cause it is scanning)--anyway, something beginning with that phrase.
You want to change the first and third items to your desired home page--then
it'll stop bugging you.
There is UI to make these settings presented when you first set up the
program, but clearly many people either ignore it or don't understand it as
it is presented.