Change it here.

setting manually the home page back to the previous one does not help. When I restart Firefox, the hijacker sets my home page back to www.iknowsearch.net again.

This happened to my wife on a PowerMac laptop - the home page is set on all of our computers for google.ca but for unexplained reasons, every time my wife opened Firefox [or Safari for that matter], even if google.ca was entered in the address bar, it automatically re-routed to search-results.com. I get infuriated by this kind of thing and I searched the web for a solution. Most of the information was for PC's and involved a lot of directory stuff, but I did see something about Proxy settings. I went to the computer's proxy settings, and there was a web address in a box that began with an asterisk (*). I deleted that, closed the options and opened a new window - problem solved! Hope this is helpful for others!