If you work with a dated version of Spybot - Search & Destroy, please update to version 1.6. You will find several download links on our download page.

If you are not immunizing with full administrator rights, Spybot-S&D might not have permission to immunize all user accounts. And if you are using Windows Vista, you should also read this FAQ entry about getting Administrator rights under Vista.

Some users who use SpySweeper or SpywareBlaster have reported that shutting down this software solves the problem. ZoneAlarm might also block the global hosts. Please click under ZoneAlarm on Firewall. Got to the main tab in the upper right, then click on the advance button. Under General settings you will see Lock Hosts file.

Further please try the following:

Open Spybot-S&D → click on Immunize → uncheck the box next to Global (Hosts) under Windows. Then click on Mode → Advanced Mode → Tools → Hosts file → then click on the Add Spybot S&D hosts list button. Then Immunize again.

The problem that not all global host entries have been immunized has also been discussed in our forum:
http://forums.spybot.info/showthread.php?t=18122&highlight=immunize+global
http://forums.spybot.info/showthread.php?t=19314&highlight=immunize+global
http://forums.spybot.info/showthread.php?t=17913&highlight=immunize+global