IE7/Firefox 3 Ignoring Hosts File & Immunizations

I've noticed over the past several weeks that both IE7 and Firefox 3 are able to set cookies and visit websites that are supposedly blocked by Spybot SDHelper and Immunizations to both browsers and the Hosts file. SDHelper is active and all 93076 (as of today, 9/02/08) immunizations report they are protected. Is it possible there is some registry setting telling Windows to ignore the hosts file or browser security settings?

Windows XP MCE SP3 (all latest updates)
Spybot S&D 1.6.0.30 (latest update 8/27/08)