I got an iMac recently. And shock horror, I think I got some kinda virus!!
(maybe I still have it, but I seemed to have cured the symptoms for now...)
What it did was was change the DNS settings, which meant evertime i tried to login to gmail or Google it would redirect me to a site called wsearch.
Nice... Really nice....
I fixed it by manually setting up my network settings - deleting the automatically inserted dns entries and lookup domains, and entering sane ones.
I gotta switch back to Linux soon!! : )