I wondered the same thing as I use Spybot. But I installed Spybot over a month ago and just started having troubles this last week.
I will add to my other post ubove:
I have to use the backward way into the site again. I can sign in and view my SPG account, but, I just tried to book a room for next week and I get all the way to the 'reserve' button and then I get the
"The page cannot be displayed" from IE again.
Maybe I will have to stay somewhere else.