Thanks Mow, I do have IFrame set to prompt, but the only 'prompt' I received was the one to have my computer 'scanned'. (?) I was using Firefox at the time though, so perhaps this works differently to IE.
I'll remember to turn off Resident protection before installing the next lot of genuine Windows updates - of which the blog on your hosts-file.net link tells there are some big ones on the way.
I was more interested in getting another hosts file. Is the one that can be downloaded from hosts-file.net recommended, and is this or another you could recommend automatically updateable?