This has happened to me a couple of times. With Spybot running, I delete the various windows\system32\drivers\etc\hosts.xxxx.backup files. Then I copy the hosts.sam file, and rename it to hosts (no . or extension, just 'hosts'). NOTE: this assumes you do not have a customized hosts file, otherwise, you can open the hosts file in notepad and delete all entries below your custom entries, and resave it.
With only Global hosts selected in the immunization window, I undo, then immunize. This has worked for me every time Spybot gets stuck on this item.
Good luck!