In versions of Spybot prior to Spybot 1.5 the addition of Spybot's Hosts file was not done in Spybot's immunization facility. To add Spybot's Hosts file in versions prior to Spybot 1.5 you had to go into Spybot – Search & Destroy > Mode > Advanced mode > Tools > Hosts file. Unless you were using the "Hosts file" facility in Spybot's "Tools" facility in prior versions, the issue would never have arisen.
Have you attempted to disable Webroot SpySweeper and then immunize the "Global (Hosts)"?