Sure you haven't got that QHost virus/trojan going around?

http://www.theregister.co.uk/content/56/33187.html

edit: Here's teh Symantec page - they have a fix tool:

http://securityresponse.symantec.com/avcenter/venc/data/trojan.qhosts.html

I think the latest "Critical" update might fix the vulnerability too. Apparently a banner on a FortuneCity site has been spreading it.

Gareth