I've been able to remove these things by hand before, when I can't find something to do it for me.. it's tricky though. I usually search the registry for something like the URL it takes you to, or search all files on the HD for that URL, and delete any and all references to it. Last one I had to do was really nasty and put something in startup that reinstalled itself (by browsing to another, separate URL).
Just thowing that out as an option
